From "For God's Sake: An Atheist, A Jew, a Christian and a Muslim Debate Religion":
Rachel Woodlock (Islam): Religion, unfortunately, provides a useful cover and powerful motivator for the evil-hearted. That religion can be so markedly different in the hands of the power-hungry, as opposed to the altruistic and virtuous, really says more about human psychology than it does about religion. That's why so many human conflicts unfortunately involve religion.
Antony Loewenstein (Judaism): I've been guilty of claiming religion is the source of the world's evils, but it's a careless comment. It's far too easy to blame the Muslim faith for honour killings. I'm under no illusion about the fact that religion is routinely used to justify the more heinous crimes. But the 20th century is filled with examples, namely Stalin's Soviet Union and Mao's China, that didn't need God as an excuse to commit genocide against a state's own people.
Jane Caro (Atheism): …human beings are generally only prepared to fight and kill in the name of something. It can be a god, but it can also be a political philosophy – like nazism or communism. Many fight for patriotism: for country, tribe or race. Some kill because they're psychologically disturbed, but none – so far – in the name of atheism. … So, while I don't agree that only religion causes conflict, I'd argue that all mass murder and war are fought in the name of a bigger-than-self philosophy or idea. Atheism, simply lack of belief in a god, has not yet proved compelling enough to motivate murder. So far no one has gone into a crowded public space and blown themselves up while shouting, "No god is great!".
Simon Smart (Christianity): Yale theologian Miroslav Volf argues that as far as Christianity goes, it will only be violent if it is stripped of its content— thinned out - and infused with a different set of values. The story of Jesus gives absolutely no warrant for violence. Any believer behaving that way is disobeying the one they claim to be following. … The answer, Volf argues, to violence perpetrated in the name of the Cross, is not less Christianity but more – Christianity that is not depleted of its meaning but full of its original moral content, which is at its heart non-violent and a force for good.
Doesn't religion cause most of the conflict in the world?