"Indeed, the presence of evil has been used, time and again, as a kind of trump card thrown down in debate against theists in general and design proponents in particular as the unanswerable objection, a lock-tight logical proof of atheism. In slightly expanded form, the logic runs as follows: If God exists, He is all-powerful and benevolent. If He is all powerful and benevolent, He wouldn't allow _____. But _____ exists; therefore, God does not exist."

A most fascinating article about the backdoor theism that tends to creep into atheism everywhere. Similar arguments apply when atheists turn out to be environmentalists. Gets a little Catholic at the end, but it's Crisis magazine, recommended anywho.