Fact, every single german nazi was a christian

[Dystopia]

Actually, atheism was a fundamental component of all those people's ideologies - Just think about it, communism was rampant back then and to be a communist you almost certainly had to be an atheist, at least on paper, so if you take atheism out of the picture that's a strong reason for the communist party to ignore you or worse, kill you, and therefore you wouldn't even have the chance to commit any crime against mankind. Many atheists think it's rationally consistent to blame Christianity or any other religion for the actions of X or Y people (even if X and Y people are fundamentally inspired by different reasons and live in different environments, for different goals etc) but suddenly when atheism plays a minor role in something it is not possible. Atheism wasn't always a lack of belief in god, it used to be a strong disbelief in deities and the adherence to strict materialism and rejection of the supernatural in its entirety. Stalin, Mao and Pol Pot didn't happen to be atheists - That's a dumb statement at worst, ignorance at best - They happened to be atheists as much as they happened to be communists. It's not comparable to the fact they had mustaches because atheism was a fundamental trait of their ideologies and was interpreted very differently compared to the modern, almost evasive and intellectually reductionist definitions of atheism.

IMO, we shouldn't even care about the argument at all - Arguably all of those people are inspiring for Marxists and setting aside poor decisions and terrible actions all of them, specially Lenin and Stalin, wrote great books - Worth a read - We keep evaluating it with a western concept of morality but it's necessary to put ourselves back in the day's mentality and cultural norms.