Morality is the heart of the issue. With the theory of evolution you have the "survival of the fittest" passing their genetics onto the next generation. It doesn't matter whether it's done morally or not, all that matters is that the genetic code is passed on to the next generation, morality be damned in regards to how it gets done.
At least with a belief in God comes some sort of moral foundation to govern human behavior, with evolution not so much. Do we want to live in world that is governed by the rules of survival of the fittest? Or a world in which has rules and governs morality? The rules to what is moral and what is not are a whole different debate. Personally I would much rather live in a world where most of us are motivated in some way to be honest and treat each each other with dignity that a world if which it's every man for himself.
"Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passion, they cannot alter the state of facts and evidence". John Adams
"A dishonest man can always be trusted to be dishonest". Captain Jack Sparrow
