Whatever the cause for why atheist regimes do what they do, the indisputable fact is that all the religions of the world put together have in three thousand years not managed to kill anywhere near the number of people killed in the name of atheism in the past few decades. It’s time to abandon the mindlessly repeated mantra that religious belief has been the main source of human conflict and violence. Atheism, not religion, is responsible for the worst mass murders of history.