Christians society has not left violence behind, we are just less likely to rationalise it with religion. Although it is not unheard of; just listen to some of the nonesense that George Bush spouted. But is is very naive to believe that violence wouldn't exist if we were all atheists and identified as skeptics.

Humans have an intrinsic capacity for violence. History is littered with examples of groups attacking someone for rape, murder and plunder and then describing it as "gods work". Probably the desire to murder and rape came before the sanctification. Why should we care what the excuse is?