But, epistemologicaly, this could take forever. I will first correct you in that Stalin and Mao were not atheists at all. Mao especially. Stalin wanted to restrict the power of "religion", but he often talked of divine intervention and that the rise of the workers was supported by "god" and the Bible. Mao claimed to be channeling the gods and declared himself a type of Christos or god-man. And, the lack of belief in a deity by itself does not cause any behavior, although it may effect behavior. For instance, I do not say the words "under God" in the pledge (added in 1954, but that is another story) - that is an effect on my behavior. But, I never, and can't even comprehend what it would mean, to "do" something purely because there is no god.
The lack of something cannot, by definition, be a cause or a motivation to act. Does that make sense?
When I used the word 'crime' I was merely carrying over something from another poster. I would say then that the crimes were murder. Anyone who orders murder, like Bush and Obama, are just as guilty as someone who pulls the trigger. Murder is wrong, as it has been for tens of thousands of years, because it deprives a person of their property, their liberty. We have learned as a species, and it is inherent in our social system, that it is detrimental. We also, being sentient beings and self-aware, have a drive to survive. So, any threat to that survival is shared among groups and tribes.
So, no, no authority is involved. It is not a "law" - it is common sense and intelligent to find murder to work against us. However, an authority is required, as in my previous referrence to the President and add in Evangelical preachers in recent years, for people to be "OK" with murder.
"In the beginning of a change the patriot is a scarce man, and brave, and hated and scorned. When his cause succeeds, the timid join him, for then it costs nothing to be a patriot."--Mark Twain