No apologies necessary, but it is important to determine what one means by "belief". One can acknowledge the existence of genocide but not believe in it, i.e., not subscribe to it. Or one can believe that something doesn't exist at all.
I suspect that most atheists just don't care. "God" may exist or not. And whether or not he does has nothing to do with how the atheist lives his life. He can live what others would consider to be a highly "moral" life or he can be a sociopath. But given the number of sociopathic or even psychopathic Christians (e.g., Dick Cheney), whether or not one believes in "God" or even the existence of same appears not to be particularly relevant to how "moral" one is.
The primary objection that atheists have to religion -- particularly Christianity -- seems to be the insistence on the part of the religious to insist that everyone -- or at least everyone else -- live according to what the religious believe is proper or correct. It's not enough for the religious to believe in whatever; everyone else must believe it as well.
Which, at least on the surface, is why we are now at war. Again.