Copy Paste bro,
you are mistaken. The Civil Wars listed were not religious wars. If you research on them, you will find other factors. The other 3 had a religious component but there were other factors such as political and economic. When you say religion kills, you have to prove that the factor is only religion and nothing else. For example a Christian killing a hindu just to promote his religion and vice versa. In all the above examples, even the opposing sides had been Atheists, the conflict would still have happened as the other factors of the wars would still have been there.
 
The good thing is that on reflection, many devout Theists will reflect on them and acknowledge the mistakes. They will say that what happened in the past was wrong. Had Stalin, Pol Pot been a devout Jesus lover or for that matter, had they been a devout Buddhist, they would not have killed. There is a possibility of that. 

What we need is for Atheists to come together and acknowledge their mistakes also. We very well know that this will never happen. That is why it is better to join a group which after making some mistakes can reflect on them, admit their mistakes and learn from them. This is how society grows to be better. Why join a group who will disown you as MAD after you have made some mistakes?.  There is no sense of Accountability then.