[physicalist]

Nazi Germany was Christian, very much so (There were also fringe pagan elements, yes). Atheists were persecuted under Hitler. Soviet Russia didn't kill anyone in the name of atheism. Atheism isn't an ideology, only the lack of a certain kind of ideology. There isn't much that unites atheists. It doesn't mean atheists don't subscribe to any ideologies, of course. In the case of Soviet Russia, the ideology responsible for the atrocities commited would be communism. Of course, these ideologies are not the sole reason people turn into savages. But Nazi Germany and Christianity for example were compatible because they shared a lot of hatred against jews. Christianity made a lot more people susceptible to Nazi propaganda (together with economic problems) than would have been possible.