Why do Communist states (e.g. USSR, China) oppose religion so much?

Question

Why did both communist people and Communist states oppose religion so much, sometimes with violence and arson. There are many other secular non-Communist states in the world that do not have such a strong hatred of and opposition to religion. They neither oppose nor support religion, and do not use extreme practices to try to eliminate it.

Communist states, particularly the Soviet Union, had tried to eradicate every bit of religion that had existed since their revolutions. China's Cultural Revolution had also attempted to eliminate remnants of traditional and capitalist elements, including historic artifacts, but also religious and cultural sites.

The Cathedral of Christ the Saviour, Moscow, during its demolition in 1931:

Chinese Cultural Revolution propaganda:

Answer 1

One aspect not explicitly mentioned by the others, and why a country like the People's Republic of China is still wary of religion it doesn't control even though it has strayed quite far from dogmatic Marxism:

The Church power is a power that is not within the control of the state or the Party. It is perceived as competing, and therefore a threat to any totalitarian regime.

For the same reason, organisations like traditional scouting are also distrusted or outright banned in totalitarian regimes: the Party provides its own mass association for kids to bond and explore nature, controlled by the Party. For example, the Freie Deutsche Jugend had this role in East Germany (it is now a tiny fringe organisation, that somehow did not get disbanded like the others). Similarly, the communists had mass organisations for sport, work (labour unions), and even allotment gardeners, all under the control of the Party.

Answer 2

TL;DR

1. The key founders of Russian Communism have openly declared that the Marxism and religion are „incompatible“. Namely, Marxism has declared the lines of conduct which are opposite to Orthodox Christianity, the most popular religion of the Russia;
2. Marxism, at least, as it has been understood by Russian Bolsheviks, was a dogmatic, non-scientific belief, hence, a direct competitor to many world's religions of the time.
3. The Russian Orthodox Church has been adopted by KGB during the times of WWII, when it became apparent that Marxist ideology is not sufficient for controlling the masses.

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Yielding the Floor to an Ideologist

First, a note on terminology.
Below, the quotes mistakenly (or deliberately) mix two terms: Marxism (an ideology) and Communism/Socialism (a ruling regime, or a type of a government). The question also contains this mistake. Communism (a regime) can't oppose religion in general, but Marxism (an ideology) can.

Nikolai Bukharin, one of the key ideologists of Russian Communism and prolific author on „revolutionary theory“, wrote in his book, The ABC of Communism (1919):

Chapter 11: Communism and Religion
§ 89. Why religion and communism are incompatible

Many weak-kneed communists reason as follows: 'Religion does not prevent my being a communist. I believe both in God and in communism. My faith in God does not hinder me from fighting for the cause of the proletarian revolution.'

This train of thought is radically false. Religion and communism are incompatible, both theoretically and practically.

In practice, no less than in theory, communism is incompatible with religious faith. The tactic of the Communist Party prescribes for the members of the party definite lines of conduct. The moral code of every religion in like manner prescribes for the faithful some definite line of conduct.

— marxists.org

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Competition

As I mention in another answer, Marxism is an ideology of class supremacy. Proletariat supposed to be the "master class", while others are "lower" ones.

However, the majority of proletarians were not familiar with Marxist ideology. There was also no goal to teach them with the details of Marxism. As a result, the vast majority of them simply believed that Marxism is right without knowing Marxist ideas in any depth, just the same way as in Tsarist Russia they believed in Christianity while sincerely thinking that Jesus Christ was a Russian, not to mention the deeper aspects of Christianity.

So, there was no place for two competing ideologies, equivalent to each other in most aspects, as it was understood by the overwhelming majority of the population.

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Adoption by KGB

However, in 1940s the Stalin's regime has decided that suppressing the religion is not effective:

After Nazi Germany's attack on the Soviet Union in 1941, Joseph Stalin revived the Russian Orthodox Church to intensify patriotic support for the war effort. — Wikipedia

By the last years of the „Soviet Union“,

"Not a single candidate for the office of bishop or any other high-ranking office, much less a member of Holy Synod, went through without confirmation by the Central Committee of the CPSU and the KGB" — Wikipedia

Nowadays, the KGB officer codename „Mikhailov“ is allegedly the leader of the Russian Orthodox Church.

Answer 3

I do not know for China but in Russia Orthodox Christianity had long tradition of supporting monarchism, schauvinism, anti-semitism, nationalism etc.

It was one of the leading sources of inspiration for pogroms, persecution and forced assimiliation of ethnic minorities crushing on the workers protests etc.

Every worker's protests were crushed with mounted thugs, often, cossacks, with whips and icons.

Black hundreds rallies:

Persecution of the Jews was also justified with religious motifs and the priests very oftern made hate speach declarations against not only Jews, but also against Ukrainians, Poles etc.

It was more or less consensus among the left at the beginning of XXth century that religion brings in inter-ethnic strife and represents danger to the inter-ethnic peace in Russia.

Answer 4

Just so it's said, in Marxist philosophy religion is generally viewed as a soporific: something which lulls to masses into believing they will be rewarded in the next life if they work hard and follow the rules in this Life. Since Marxism aims at waking people up — making them realize the exploited condition of their lives in the here and now — they tend to see religion as a hinderance. Marxism isn't anti-religious per se, much less anti-spiritual or anti-theistic, but it opposes any theology that tries to wish away the suffering of the laboring class, because such theology undercuts the Marxist trajectory.

There are and have been many religious groups that have promoted and worked for Marxist principles. Such groups simply reach for eternal salvation through social progress.

Answer 5

I think people seem to forget that socialist regimes are not always hostile to religion and sometimes form alliances with religious socialists. The USSR recognized Libya under Muammar al-Gaddafi due to his own ideology that was a form of state socialism tied to Islam. People seem to forget that throughout a lot of history in Europe & certain parts of Asia, religion was used as a tool of power and a way to get wealthy easily or have a higher societal position by using a God as a tool for political accession. In France before the French Revolution, for example, clergy were members of the First Estate that could levy a ten percent tax on the peasants 'in the name of God' whenever they feel like it before doing whatever they want with the money. Then, you have the entirety of feudalism where kings ruled due to the 'divine right of kings'.

From a Marxist and European socialist perspective, religion is often used as a tool of feudalists, capitalists, and enemies of the proletariat to gain wealth and power over the common worker. Positions also would depend on whether you believed in the 'correct faith' or not. In most authoritarian socialist states, any worker or member of the community could work their way up to a higher position in society (and at least in theory, the state is supposed to be a temporary means to an end to protect from capitalist counter-revolutionaries and guide people towards a stateless, moneyless society that would be achieved once society became advanced enough & the state would naturally erode away or be dealt with in a final revolution). So, a lot of the animosity to religion was due to it being connected to classist systems at various points in history and its use frequently as a way to maintain classist systems generally opposed to what socialist states aim to accomplish: a stateless, moneyless society that is supposed to form after the defeat of capitalism and other anti-socialist systems.

Answer 6

I do not know if it must always be this way but in Soviet system Atheism was an important part of the Communism ideology. The vision was that people will work for free because they enjoy working, it is interesting to work, because an attractive work is important part of self-realization, work is where you communicate with other people the most, hence the work is the important part of the meaning of life. This somewhat clashes with religions that may not be very against the hard work yet put completely different reasons for living. Soviets published many books for teenagers where this disagreement is addressed (atheistic propaganda was mainstream).

It was never obvious who will motivate people working in non-creative professions, but some Soviet science fiction (like Andromeda Nebula by I.Yefremov) describe the society where people swap the professions every few years, doing tasks nobody particularly likes in shifts and find creative and interesting aspects in professions that are generally not seen as very creative. Also, it was expected that the amount of boring work will decline with the advance of technology.

Answer 7

Since communism is based on the theory by Marx, it is called opium of the people and drugs are ilegal in most states. So forbiding religion in this context could be seen juas as forbiding an other drug. In this context it is more important how people in countries like USSR and China understood that statement and not what Marx really meaned.

In countries like USSR, Chine and specially North Korea there was and sometimes still is the cult of personality, where the first communist leader of the country is seen as some kind of god. This is defenetly is not compatible with the most religions specialy christian but also judais and islam.

Also at least at some early stage it seems that Lenin was not really wanting to forbid religion, religion should just be kept out of the state as can be read in his work from 1905.