In my answer I will refer to “female genital cutting” (FGC), instead of FGM. For reasons why, refer to [22] and [28]. Suffice to say – Many women who *have* had their genitalia cut do not feel “mutilated”, and feel this is a value-laden term which they would rather not have applied to their bodies, and it leads to stigma and shame [22]. I choose to respect these women’s wishes, given their voice is not often heard. Furthermore [22], this term does actual, active harm to women who have been cut.

A TLDR (without citations, citations are found in the more extensive answer):

 1. Across much of the western world knowledge about the form and reasons for FGC is poor, relying on poorly-research and unsubstantiated tropes. It is perceived that western reasons for male circumcision are "medical" and "civilised" whilst FGC is done for "barbaric" reasons.
 2. A "zero-tolerance" approach to FGM has been adopted by the UN/WHO, and is incorporated into western law. This bans *all* forms of FGC, however minor or medicalized, as a human rights violation, as it denies girls bodily autonomy and integrity. (The author believes this to be correct path to take, but suggests that such an argument should logically extend to intersex & male children also).
 3. Anthropologists have found deep parallels between FGC and male circumcision across cultures. Both encompass a spectrum of practices of varying severity, with the two practices commonly serve as parallel "initiation" rites into adulthood. Women with FGC will often (although not always) consider their genitalia to have been enhanced and beautified by the practice. FGC serves to transition girls into women and earns them the respect of their elders and peers.  
 4. The connection of FGC to patriarchy is poorly-established. In almost all societies practising FGC, MC is also performed [1] - girls are not "singled out" for genital cutting. In most societies FGC is performed and upheld by women. In many societies men oppose the continuation of FGC, whilst women continue to support it. In only a relatively few countries (Sudan, Somalia, Djibouti) is the connection of the most extreme form of FGC (infibulation) connected to problematic social norms regarding female sexuality. Patriarchy is not a good explanation for FGC - for example the Kikuyu in Kenya, and women in Sierra Leone are not oppressed sexually - there is no cultural obsession with female chastity/virginity - yet undergo FGC as a form of initiation.
 5. Male circumcision is considerably more invasive than minor forms of FGC which are performed for analogous reasons. In the Dawoodi Bohra sect of Islam both boys and girls are "circumcised" to mark their presence in the Abrahamic covenenant. The cutting for girls consists of a ritual nick with no removal of flesh, whereas for boys it entails removal of the foreskin. Notably the first FGM case in the US concerned Dr Jumana Nagarwala of the Dawoodi Bohra, on trial for performing this type of FGC. 
 6. Cultural bias (particularly in the US) prevents recognition of the parallels between the practices. This culture bias is most pronounced in English-speaking countries, where neonatal circumcision was routine (and still is in USA), where law-makers themselves are typically circumcised. Throughout history people have acccepted their own childhood bodily modifications, whilst rejecting those of "foreign" cultures. (Chinese foot-binding, ritual scarification/tatooing of minors, corsetting etc.) There is a tendency to rationalise familiar practices, whilst rejecting foreign practices (the so-called "yuck" factor). Male circumcision has been widely practised in the West, at first by Jews, then starting in the 1900s in the anglosphere - UK, USA, NZ, AUS. In modern times both Jews and Muslims practice MC, and it is difficult to see how any Western nation could ban MC without causing significant outcry from these 2 groups (see Machavity's answer for this idea). FGC is seen as an "outsider" & "barbaric" custom and so is readily prohibited, whereas MC is a "familiar" custom and the parallels are generally ignored.
 7. Adding to this "firewall" between FGC and MC was the work of Fran Hosken a feminist in the 1970s who authored the "Hosken Report" on FGC/M. In the 70s there was a movement in Western feminism to establish the idea of a "global sisterhood". Fran Hosken believed that FGM would provide an iron-cast representation of the global patriarchal oppression of women. At the time knowledge of this practice was poor, and largely limited to Sudan/Somalia where the most extreme form of FGC (infibulation) is practised and closely linked to the (highly problematic) Purdah ideology of the particular form of Islam followed there. This paradigm seemed to stick, despite criticisms over the following decades from anthropologists that this could not be generalised to all forms of FGC, and indeed that patriarchy is not a good explanation for FGC.
 8. The firewall between FGC and MC may be breaking down, as recognition of the potential harms of MC, and recognition of the prevalence of minor, medicalized forms of FGC increases. These forms are prevalent across SE Asia in the Muslim populations of Malaysia, Indonesia and Singapore, where an estimated 60-70 million girls/women have had a "minor" form of FGC performed on them.
 9. The political ramifications of this are likely to play out differently in different countries. Countries in Northern Europe already recognise the harms of MC, and seem likely to further censure it, with the aim of procuring a total ban when this is deemed safe. (Indeed Iceland and Finland have already had attempts at a ban). In USA, it seems more likely that minor, medicalized forms of FGC will be legalised, as the parallel to the culturally endemic MC are recognised (as seen in the 1st FGM trial in the US, where the federal FGM bill was struck down as unconstitutional, for further analysis see: https://www.youtube.com/watch?v=GBH0g_Cl7Rk).

The longer version of my answer follows:

Firstly to address the question most directly -  The WHO and UN definition of FGM (incorporated into law across the developed world) encompass *any* cutting done to a girls’ genitalia without medical necessity. This is a key point – the “zero tolerance” approach promoted by UN/WHO, and which has been adopted into the laws on FGM in western nations, means that *any* cutting done to a girl’s genitalia is classified as FGM, condemned as a human rights abuse, and is illegal. On this basis, there simply *is* a discrepancy in the law, as male circumcision, *if* performed on a girl, would indeed be illegal. I'm not sure that there is really any debate here - US law, and the UN/WHO stance which has been incorporated into pretty much all laws on FGM in the West and around the world rules out *any* form of female genital cutting (FGC), even those forms that are less invasive than male circumcision. This is particularly pertinent when it is considered that the first prosecution sought under the US FGM law was the prosecution of Dr Jamala Nagarwala, a physician who was also a member of the Dawoodi Bohra sect of Islam. The Bohra "circumcise" both their boys and girls for the same reason - as an induction into the Abrahamic covenant. They hold this as one of the "innovations" of Mohammed - to introduce a gender-neutral ritual marking out membership of the covenant. Indeed the Bohra are known for their egalitarianism - both men and women hold leadership roles, both men and women are highly educated and both men and women will frequently find employment as lawyers and physicians. For the Bohra the cutting performed on girls is called "khatna" and consists of a "ritual nick" to the clitoral hood removing no flesh. On any account this is far less invasive than male circumcision, as it removes no flesh, and usually leaves no permanent scar. Above answers have failed to take into account that this is the *only* instance where US law has been brought to bear on FGM. I am not sure why this has be omitted from consideration, and perhaps other answerers would like to take this into account in their answers.

I shall now move onto a somewhat broader discourse on FGC and MC. 

The roots of the current paradigm which separates FGC and MC into two separate discussions, and the idea that FGC and MC are fundamentally incomparable stems from the 1970s, and can largely be attributed to Fran Hosken's work. In the 1970s there was a push within Western feminism to push for a "global sisterhood". Fran Hosken believed that FGC/M was a iron-cast example of a global patriarchy oppressing women. At the time the knowledge about FGC was poor, and largely restricted to Sudan/Somalia (the East Nile region) (Obermeyers comments below, [5]). On these two examples there was indeed a good case to be made for FGC being an instrument of an oppressive patriarchy. At the time anthropologists warned against taking a universal approach, saying that gender roles vary significantly from culture to culture. 

This paradigm stuck, and once this paradigm was established it has become largely impervious to criticism. One of my sources which I recommend to anybody is "Seven things to know about female genital surgeries in Africa". This is a Hastings Centre Report published by 15 international experts in FGC. The authors/signatories consist of a number of obstericians/gynaecologists who are senior physicians running clinics for women with FGC (Birgitta Essen, Lucrezia Catania, Jasmine Abdulcadir) a number of anthropologists (Sara Johnsdotter works closely with Essen, Fuambai Sia Ahmadu and Richard Schweder have worked together frequently, Shell-Duncan is also an anthropologist) along with other legal experts and feminists. These authors advocate for vastly different policies elsewhere  - the obstericians are against FGC, Abdulcadir and Johnsdotter were both signatories to "Medically Unnecessary Genital Cutting and the Rights of the Child: Moving Toward Consensus" which suggested that *all* medically unnecessary cutting of children's genitals should be viewed as impermissible; Ahmadu and Schweder advocate for a far more liberal treatment of FGC. Despite this all agreed to be signatories to this document which provides an evidence-based quantification of the harms of FGC, an evidence-based account of the varying motives for FGC, and suggests that the mainstream view of FGC is overly sensationalised and poorly substantiated. This document was published a few months in advance of a WHO meeting on FGM with the aim of encouraging an evidence-based approach. They worried that misconceptions about FGC were harming women with FGC living in Western nations, and believed that an evidence-based approach was more appropriate. This report was generally ignored, despite the expertise of the 4 gynaecologists who treat women with FGC, and the expertise of Johnsdotter and Shell-Duncan who report that the motives for FGC are varied and that patriarchy is a poor explanation. 

To unpack this a bit more - In the past few decades anthropologists have found that FGC is a more widespread custom than originally thought in the 1970s and found that male circumcision and FGC are in fact far more similar than many people would think. In most societies which practice FGC it is performed by women and upheld by women [1] - it is "women's business". 

The perception that FGC is associated strongly with patriarchy and male suppression of female sexuality is not well-established [1]:
 
> “The empirical association between patriarchy and genital surgeries is
> not well established. The vast majority of the world’s societies can
> be described as patriarchal, and most either do not modify the
> genitals of either sex or modify the genitals of males only. There are
> almost no patriarchal societies with customary genital surgeries for
> females only. Across human societies there is a broad range of
> cultural attitudes concerning female sexuality—from societies that
> press for temperance, restraint, and the control of sexuality to those
> that are more permissive and encouraging of sexual adventures and
> experimentation—but these differences do not correlate strongly with
> the presence or absence of female genital surgeries.”

In almost all cultures which practice FGC, it is done by women, who typically see it as hygienic, beautifying and an important rite of passage with cultural value[7,8,9,10]. 

The reasons give for it vary - in a select few cases such as Sudan/Somalia/Djibouti it is done to control women's sexuality [1]. It seems that this form of FGC is practised is due to the extreme Purdah belief in these Islamic states. These examples are often over-emphasised in accounts [5], and this paradigm has been assumed to extend to all forms of FGC. 

In other cultures such as the Kikuyu in Kenya and the Kono in Sierra Leone, there is no such emphasis on female chastity/virginity. The anthropologist Fuambia Sia Ahmadu writes that amongst the Kono tribe in Sierra Leone[7]: 

> "there is no cultural obsession with feminine chastity, virginity, or
> women’s sexual fidelity, perhaps because the role of the biological
> father is considered marginal and peripheral to the central
> ‘matricentric unit.’ … Kono culture promulgates a dual-sex ideology …
> [The] power of Bundu, the women’s secret sodality [i.e., initiation
> society that manages FGC ceremonies], suggest positive links between
> excision, women’s religious ideology, their power in domestic
> relations, and their high profile in the ‘public arena."

More broadly it seems that FGC and MC are practised as parallel imitation rites. The flesh foreskin is seen as a "female" part, the phallic external clitoris is seen as a "male" part. In order to become fully male/female these female/male elements must be removed [7].

Globally, anthropologists have found that FGC is a wide range of practices across many disparate cultures [1,2,5,7], with varying levels of invasiveness and varying cultural justifications. Severe forms of cutting are rare[1], with more minor forms of cutting being more standard. In Malaysia and Indonesia[2,3,4] the clitoral hood is nicked/pricked, and usually little/no tissue is removed. There are “no significant health related risks and physical examination failed to show any evidence of injury to the clitoris nor the labia and no signs of excised tissue”. This is not purely a pedantic point – this is one of the more common forms of FGC with around 60-70 million cases across SE Asia - Indonesia, Malaysia and Singapore.

It is worth noting that across Africa a range of practices are performed – from the most severe (infibulation), through less severe (clitoridectomy), to far more minor practices (so called “sunat”). In the Sudan and Somalia, the cutting *has* moved from a rather severe practice (infibulation), to increasingly minor and medicalized forms (such as “sunat”) as a result of a “harm-minimization” approach by some activists[6,15]. However minor or medicalised the cutting is, it is still classified as FGM by all international bodies, and the law in all developed countries. Reasons for this are addressed later. In all cultures which practice FGC, males are also cut, usually in the same conditions for parallel reasons. For males this can result in death and deformity [19,20], just the same as FGC. 

To conclude in the words of the anthropologist Zachary Aldrous [13]: 

> “The fact of the matter is that what’s done to some girls [in some
> cultures] is worse than what’s done to some boys, and what’s done to
> some boys [in some cultures] is worse than what’s done to some girls.
> By collapsing all of the many different types of procedures performed
> into a single set for each sex, categories are created that do not
> accurately describe any situation that actually occurs anywhere in the
> world.”

Another common misconception is that women subject to FGC are rendered incapable of experiencing sexual pleasure. This varies with the severity of cutting [5], but as remarked by Sara Johnsdotter [14] there is no “one-to-one” correspondence of the severity of cutting to sexual pleasure experienced. Even women cut in the most severe manner can still experience sexual pleasure [14,16,22]. [16] is a study (by some of the authors of [1] above) on women who have had infibulation performed on them, the results show: 

> “58 mutilated young women reported orgasm in 91.43%, always 8.57%;
> after defibulation 14 out of 15 infibulated women reported orgasm; the
> group of 57 infibulated women investigated with the FSFI questionnaire
> showed significant differences between group of study and an
> equivalent group of control in desire, arousal, orgasm, and
> satisfaction with mean scores higher in the group of mutilated women.
> No significant differences were observed between the two groups in
> lubrication and pain.”

 And the study concludes: 

> “embryology, anatomy, and physiology of female erectile organs are
> neglected in specialist textbooks. In infibulated women, some erectile
> structures fundamental for orgasm have not been excised. Cultural
> influence can change the perception of pleasure, as well as social
> acceptance. Every woman has the right to have sexual health and to
> feel sexual pleasure for full psychophysical well-being of the person.
> In accordance with other research, the present study reports that
> FGM/C women can also have the possibility of reaching an orgasm.
> Therefore, FGM/C women with sexual dysfunctions can and must be cured;
> they have the right to have an appropriate sexual therapy.”

On the possibility of male circumcision harming sexual it is worth noting that the foreskin is itself richly endowed with sensory nerves [17], and there does appear to be some link with sexual dysfunction, though this is disputed [18]. Again, as Sara Johnsdotter remarks [14], there appears to be no one-to-one mapping of tissue removed onto sexual pleasure/dysfunction. Instead the picture is a more complex and nuanced one. A large determining factor is whether or not that person is happy with their cut genitalia or not, and hence an international assembly has proposed a human rights argument against *all* (male, female and intersex) genital cutting practices [21].

The difference in perception was remarked upon by Hanny Lightfoot-Klein (a renowned anti-FGM activist) [23]:

> “… the mainstream anti-FGC position is premised upon an orientalizing
> construction of FGC societies as primitive, patriarchal, and barbaric,
> and of female circumcision as a harmful, unnecessary cultural practice
> based on patriarchal gender norms and ritualistic beliefs. …
> Lambasting African societies and practices (while failing to critique
> similar practices in the United States) … essentially implies that
> North American understandings of the body are “scientific” (i.e.,
> rational, civilized, and based on universally acknowledged expertise),
> while African understandings are “cultural” (i.e., superstitious,
> un-civilized, and based on false, socially constructed beliefs). [Yet]
> neither of these depictions is accurate. North American medicine is
> not free of cultural influence, and FGC practices are not bound by
> culture—at least not in the uniform way imagined by opponents.”

In America (and a number of English speaking countries) male circumcision was a widespread practice in the 20th Century. In America today, male circumcision is still a widespread, common practice, with around 50-60% of newborn males undergoing it. Across the west in general there are substantial Jewish and Muslim minorities, who practice male circumcision for religious/cultural reasons. It is this familiarity, along with political pressure from religious minorities in the face of any restrictions, which has led to male circumcision being a normalised, accepted practice across the west. It is easier to condemn a “foreign” practice such as FGC than a practice which is familiarised. Parallels to Chinese foot-binding, facial scarification and other bodily modifications imposed on children can be made – we are quick to judge other cultures for their particular form of bodily modification, whilst judging our own such bodily modifications to be” normal” and “natural”.

To address some points that Ron McMaimon made in his answer on the issue of health benefits/risks - Whilst it is true that male circumcision has some health benefits – most notably a lower chance of contracting HIV from heterosexual sex – across much of the industrialized world these health benefits are not deemed sufficient justification to recommend male circumcision. A large reason for this is – the health benefits mostly apply only to sexually active adults, and can be obtained in far less invasive ways (condoms, practicing safe sex). It is a fundamental tenet of medical ethics that the risks surgery are only justified when there is no less invasive way of treating the pathology. The presence of a foreskin is not a pathological defect, it is natural tissue. The KNMG (Royal Dutch Medical Society, Netherlands) states [29]: 

> “There are good reasons for a legal prohibition of non-therapeutic
> circumcision of male minors, as exists for female genital mutilation.
> However, the KNMG fears that a legal prohibition would result in the
> intervention being performed by non-medically qualified individuals in
> circumstances in which the quality of the intervention could not be
> sufficiently guaranteed. This could lead to more serious complications
> than is currently the case.”

On the matter of health benefits they also state – 

> “There is no convincing evidence that circumcision is useful or
> necessary in terms of prevention or hygiene. Partly in the light of
> the complications which can arise during or after circumcision,
> circumcision is not justifiable except on medical/therapeutic grounds.
> Insofar as there are medical benefits, such as a possibly reduced risk
> of HIV infection, it is reasonable to put off circumcision until the
> age at which such a risk is relevant and the boy himself can decide
> about the intervention, or can opt for any available alternatives.”

The evidence available to both European and American health professionals are the same, and yet they reach opposite conclusions. Additionally, across both China, Japan and South America, male infant circumcision is not recommended on health grounds. The US stands alone in this matter and it has been suggested that the US in particular is biased (Hanny Lightfoot-Klein above) in their perception of the medical evidence by the high rate of male circumcision in the US. In response to the promotion of male circumcision in America, a number of health professionals across Northern Europe published a response, stating they believe the American view is seriously biased [30]: 

> "Seen from the outside, cultural bias reflecting the normality of
> nontherapeutic male circumcision in the United States seems
> obvious,[…] the report’s conclusions are different from those reached[
> …] in other parts of the Western world, including Europe, Canada, and
> Australia. […], only 1 of the arguments put forward by the American
> Academy of Pediatrics has some theoretical […]; namely, the possible
> protection against urinary tract infections in infant boys, which can
> easily be treated with antibiotics without tissue loss. The other
> claimed health benefits, including protection against HIV/AIDS,
> genital herpes, genital warts, and penile cancer, are questionable,
> weak, and likely to have little public health relevance in a Western
> context, and they do not represent compelling reasons for surgery
> before boys are old enough to decide for themselves.”

It is worth bearing in mind that the default for any medical professional should be to be opposed to unnecessary surgery due to fundamental tenet of medical ethics. And to conclude with,  I quote their statement on the justifiability and ethics of prophylactic surgery [30]: 

> “The most important criteria for the justification of medical
> procedures are necessity, cost-effectiveness, subsidiarity,
> proportionality, and consent. For preventive medical procedures, this
> means that the procedure must effectively lead to the prevention of a
> serious medical problem, that there is no less intrusive means of
> reaching the same goal, and that the risks of the procedure are
> proportional to the intended benefit. In addition, when performed in
> childhood, it needs to be clearly demonstrated that it is essential to
> perform the procedure before an age at which the individual can make a
> decision about the procedure for him or herself.”

Some comments to clear up any possible misconceptions about my stance on the acceptability of non-therapeutic genital alterations of children - I am against *any* cutting of a child's genitals, barring medical necessity. It is a persistent struggle to change the minds of women who perform FGC on their daughters, when they will ask “Why is this wrong, but Americans circumcising their children is fine?” They ask this because they see these two practices as one and the same – cutting cultures almost invariably see MGC and FGC as two sides of the same coin. It proves significantly harder to end FGC if male circumcision is seen as acceptable. Moreover – the ethical arguments proposed for why FGC is wrong, *also* apply to male circumcision. If we are to declare bodily autonomy and integrity as human rights, they apply to *all* humans -  male, female and intersex. And if we wish to judge other cultures, we should check that our culture is consistent with the measure we use. 

Finally - MC as practised globally takes many forms, many of which are dangerous (Ulwalako in S. Africa regularly kills & maims dozens of boys); similarly dangerous circumcisions occur across Africa; Tuli in the Philippines consists of 10y/o boys being pinned to tables and circumcised in public causing PTSD in ~70% of cases; forced circumcisions (see Kenya & elsewhere) can result in amputation. The harmless image of MC in the West is because the West is highly medicalised, so we picture MC as safe & sterile, and picture FGC as unsafe. 


The main citation for the (likely controversial claims on FGC) can be found here: (this is citation 1 - “Seven Things to Know about Female Genital Surgeries in Africa.” Hastings Center Report)

https://www.sfog.se/media/295486/omskarelse_rapport.pdf


Citations:
[1] “Seven Things to Know about Female Genital Surgeries in Africa.” Hastings Center Report, vol. 42, no. 6, 2012, pp. 19–27., doi:10.1002/hast.81.

[4] Rashid, Abdul, and Yufu Iguchi. “Female Genital Cutting in Malaysia: a Mixed-Methods Study.” BMJ Open, vol. 9, no. 4, 2019, doi:10.1136/bmjopen-2018-025078.

[5] Obermeyer CM, Reynolds RF. Female genital surgeries, reproductive health and sexuality: a review of the evidence. Reproductive Health Matters1999;7:112–20.

[11] Shweder, Richard A. “The Goose and the Gander: the Genital Wars.” Circumcision, Public Health, Genital Autonomy and Cultural Rights, May 2017, pp. 141–159., doi:10.4324/9781315095684-16.


[12] Davis DS. Male and female genital alteration: a collision course with the law. Health Matrix. 2001;11:487–687.


[13] Androus ZT. The United States, FGM, and Global Rights to Bodily Integrity. Paper presented at The Rothermere American Institute Conference: The United States and Global Human Rights. November, 2004. Oxford University. Available at http://www.zacharyandrous.com/The%20US%20FGM%20and%20Global%20HR.pdf.

[14] Johnsdotter, Sara. “Discourses on Sexual Pleasure after Genital Modifications: the Fallacy of Genital Determinism (a Response to J. Steven Svoboda).” Circumcision, Public Health, Genital Autonomy and Cultural Rights, May 2017, pp. 46–55., doi:10.4324/9781315095684-6.

[16]Catania L, Abdulcadir O, Puppo V, Verde JB, Abdulcadir J, Abdulcadir D. Pleasure and orgasm in women with female genital mutilation/cutting (FGM/C). The Journal of Sexual Medicine. 2007;4(6):1666–1678.

[19] http://allafrica.com/stories/201406251112.html. http://ulwaluko.co.za/

[21] “Medically Unnecessary Genital Cutting and the Rights of the Child: Moving Toward Consensus.” The American Journal of Bioethics, vol. 19, no. 10, 2019, pp. 17–28., doi:10.1080/15265161.2019.1643945.

[22] Earp, Brian D. “Protecting Children from Medically Unnecessary Genital Cutting Without Stigmatizing Women’s Bodies: Implications for Sexual Pleasure and Pain.” Archives of Sexual Behavior, 2020, doi:10.1007/s10508-020-01633-x.

[23] Lightfoot-Klein, Hanny. “Similarities in Attitudes and Misconceptions about Male and Female Sexual Mutilations.” Sexual Mutilations, 1997, pp. 131–135., doi:10.1007/978-1-4757-2679-4_12.

[25] Earp, Brian & Shaw, David. (2017). Cultural bias in American medicine: the case of infant male circumcision. Journal of Pediatric Ethics. 1. 8-26.

[26] Earp, Brian & Shaw, David. (2017). Cultural bias in American medicine: the case of infant male circumcision. Journal of Pediatric Ethics. 1. 8-26.

[27] Earp, Brian. (2020). Gender or genital autonomy? Why framing nontherapeutic genital cutting as a children's rights issue is both ethically and pragmatically necessary.

[28] Cook, R.j, et al. “Female Genital Cutting (Mutilation/Circumcision): Ethical and Legal Dimensions.” International Journal of Gynecology & Obstetrics, vol. 79, no. 3, 2002, pp. 281–287., doi:10.1016/s0020-7292(02)00277-1.

[29] https://www.knmg.nl/circumcision/

[30] http://artemide.bioeng.washington.edu/InformationIsPower/Pediatrics-2013-Frisch-peds.2012-2896.pdf