Well Done Mr. Deity.
One minor note in regards to the charge made by Christians of the atrocities committed by atheist regimes; the response of "But they didn't do in the name of atheism" or "They also all had mustaches, therefore mustaches are evil" don't address the point of the accusations. For Christians, because these atheist leaders didn't believe in god, they lacked the moral compass and therefore genocide was permitted. With this in mind, the responses above ring hollow for the Christian.
My preferred approach is to point out that atheism does not NECESSARILY lead to genocide. That is to say that committing an act of mass murder does not directly follow from accepting the proposition that there are no gods. There must be additional beliefs, on top of atheism, in order for genocide to be logical outcome. The BEST the Christian can say is that genocide is consistent with atheism, which isn't saying much since atheism is simply a single stance in regards to one proposition. Every belief EXCEPT believing a god exists is consistent with atheism. But by granting this, the Christian must also therefore grant that genocide is also consistent, and more often practiced, with theism.
I'd be happy to hear what others have to say on this.