According to Conservapedia, moral depravity is a common cause of atheism:
Moral depravity: The history of the atheist community and various studies regarding the atheist community point to moral depravity being a causal factor for atheism. In addition, there is the historical matter of deceit being used in a major way to propagate atheism from the time of Charles Darwin onward. Also, Bible exegesis points to the moral depravity of atheists. Moral depravity is certainly one of the prime causes of atheism.
So now you know :-)
One thing about Conservapedia: I never know whether a particular section has been written by a right wing nutjob, or by someone parodying them.
(via Friendly Atheist)