Furthermore, there is a HUGE difference between the intent behind the murders committed by Stalin/Mao (who were atheists) vis-a-vis the ones committed by religious crusades/jihads/inquisition/pogroms/terrorism etc etc
The difference is that in the religious wars people were targeted because of their religion/or lack of one. The mass murders by Stalin and Mao were not targeted at any specific religious/non religious denomination. They murdered indiscriminately, which can be seen as ethnic/cultural wars rather than an "atheist" war. When did anyone get killed because he was a 'religious" person by atheists? Mao and Stalin are no different from some deranged person who shoots people in the mall, albeit in a larger scale.
There is no evidence to associate atheism with the actions carried out by Mao and Stalin. Atheists don't have a "religious high command"/affiliation/branch or whatever....therefore individual actions by atheists are just that, actions of individuals. I didn't hear Stalin claiming that he is killing people in the name of "the universal church of atheism"..did you?
religions on the other hand, when engaging in wars, take the "Kill them all, God will know his own" attitude.