I am not religious but can’t agree with this common believe about religion. You can use religion in both ways: to kill and to heal and yes, people use religion often to justify the killing, but the real driving force even if it is subconscious usually is not in the realm of religion. Do you think atheists would have any difficulties to justify wars, genocide if they want to? They will come with other pseudo religious or even “scientific” theories. We have seen plenty of this in our recent history. Read Jonathan Swift what reason can be used to wage a war.
Another great point. I will list a few murdering atheists:
Stalin - Stalin the Atheist had no problem killing millions between his various purges, political killings, starvation of the 5 million Ukrainians alone in the 30's etc...I think he is responsible for the deaths of 30 million. Of course this doesn't count the murder of 10 million in his own military and 15 million civilians because of his unpreparedness in WWII. This was due to neglect, incompetence, purging his best generals prior to WWII, and his trust of Hitler of whom he signed a non-aggression pact with in the late 30's. If it weren't for the Arsenal of Democracy (the United States for you leftists) and a few bad moves by Hitler the Russians would be eating sausage and drinking beer.
Mao Tse Tung - the other great Atheists - was responsible for the deaths of 50 million.
Of course it can be argued that in the case of these two demigods they set themselves up as their own religion.