I don't see how communism or Nazism should or could be owned on Atheism. Atheism isn't full of content it is just not believing in religious claims. Sure, some atheists get passionate about there non-belief, but may of us aren't particularly concerned what others believe so long as it isn't obviously harmful.

At the moment some religions are causing harm, explicitly for religious reasons. Being an atheist in Sweden or England in my case, or anywhere doesn't mean your society will inevitably involve into sheep fucking and genocide.

You get your morality from your human nature, most humans have innately, they want the best for those they care about. Psychopaths obviously exist but the Ten Commandments never deterred any serial killer.

I don't see actions evil actions motivated purely by atheism. Atheism isn't a belief. My parents didn't raise me with the doctrines and dogmas, I wasn't told stories, asked to read books and sent to church, synagogue or mosque. They didn't need to invent new dogmas, doctrines, books and houses of atheism to replace faith with. Faith isn't necessary, at least not faith in an invisible deity that can't be seen.