Because it allows them to signal how much better they are than all those dumb nasty white rubes who believe in a "Sky God", "Sky Wizard" or whatever unoriginal name they come up with for the Christian God.
To them it's not a personal belief they're strident in so much as it is status signaling. Being an atheist or some sort of hippie pagan is a required part of joining their group, but in reality their atheism is just anti-Christian belief. They will attack anyone who criticizes any other religion that isn't primarily followed by white people. That's why they attack easy targets like Scientology and Christianity yet try to avoid Islam, Buddhism, etc.
To them it's not a personal belief they're strident in so much as it is status signaling. Being an atheist or some sort of hippie pagan is a required part of joining their group, but in reality their atheism is just anti-Christian belief. They will attack anyone who criticizes any other religion that isn't primarily followed by white people. That's why they attack easy targets like Scientology and Christianity yet try to avoid Islam, Buddhism, etc.
"Men willingly believe what they wish." - Julius Caesar, De Bello Gallico, Book III, Ch. 18