I always hear of this belief of a "War on Christmas" motivating people to vote against Democrats in the United States. What causes people to believe there is this "War on Christmas"?
What we think of as the 'War on Christmas' had its start in the very foundations of our country, as the Puritans felt the promulgation of pagan 'Yule' symbols like pine trees, Yule log, mistletoe, etc. should not be associated with the birth of Jesus Christ. For that reason (and many, many others), the creation of the United States of America pointedly avoided having an 'official' or 'sanctioned' religion, instead focusing on the 'arm's length principle' lauded by Utilitarians: I am free to swing my arms wherever I like right up until my arms hit someone else. Basically: I can practice religion all I want right up until I start trying to compel somebody else to do the same.
At first, this only applied to the Federal government, which suited the States just fine, given their wide array of faiths. But in 1947, Everson v Board of Education mandated that individual states not do official acts on behalf of any one religion; in this case, using public funds to transport private religious schoolchildren to their school.
By the 50's, the Cold War was brewing, and many religious conservatives saw separation of church and state to be downright Communist. From the pamphlet, "There goes Christmas?!":
The UN fanatics launched their assault on Christmas in 1958, but too late to get very far before the holy day was at hand. They are already busy, however, at this very moment, on efforts to poison the 1959 Christmas season with their high-pressure propaganda. What they now want to put over on the American people is simply this: Department stores throughout the country are to utilize UN symbols and emblems as Christmas decorations.
In 1962 via Engel v Vitale, the Supreme Court said that individual (public) schools couldn't compose a school prayer and force children to recite it.
In 1968, Epperson v Arkansas ruled that Arkansas couldn't ban the teaching of evolution on religious grounds. Supreme Court case after case reaffirmed: you can practice your religion however you want, just don't force others to participate and don't force taxpayers to pay for it.
Between the 1970s and 2005, conservatives railed against the idea of 'Political Correctness' by claiming an anti-religion bias. Bill O'Reilly famously claimed that the government was trying to ban the use of the word 'Christmas' to avoid offending other religions. Hate groups like the AFA jumped onto the bandwagon, threatening boycotts of any retailer that didn't conform to its religious standards, and posting a yearly 'Naughty or Nice List' of offenders. Starbucks famously made the list in 2015 for its coffee cup that didn't say 'Merry Christmas' on it.
Bottom line, it's fear of the unknown. America is changing demographics, religiosity, and level of globalization. White, Anglo-Saxon Protestants used to be at the top of the heap, so equality scares them. They'd rather think of themselves as victims than as perpetrators of policies that marginalized religious minorities. And frankly, in an increasingly secularized world, it makes them feel good to think they're fighting against some nebulous 'man' to prevent the destruction of Christianity.
The things I've seen most commonly cited as "attacks on Christmas" include the following:
- The use of the phrase "Happy Holidays", to include other celebrations held around the Christmas period such as Hanukkah and Kwanzaa, instead of "Merry Christmas".
- Starbucks have been releasing annual Christmas-themed cup designs every year since 1997. In 2015 they released a plain red design with no overt Christmas imagery, in an attempt to be more inclusive of other holidays, leading a number of conservative commentators (including Donald Trump) to call it part of the "war on Christmas". Their 2016 design, a green design with a mosaic of faces, prompted similar controversy. [Source]
- Several Christmas staples have come under scrutiny in recent years. There is the perennial argument over whether "Baby, It's Cold Outside" is about date rape, or merely a woman playing coy because of societal expectations at the time it was written. "Rudolph The Red-Nosed Reindeer" (mainly the animated special) is seen as promoting the message that "deviation from the norm will be punished unless it is exploitable". I don't know how popular the song is in America, but in the UK there have been controversies over "Fairytale of New York" and its use of the words "slut" and "f*ggot" in the second verse.
Whether any of these things constitute a "War on Christmas" or not is subjective, and beyond the scope of the question.