I'm sure we've all heard of Pascal's Wager in some form. The general logic runs that "if there is no God, then what I believe holds no consequence, but if there IS a God, then believing in Him is a significant net benefit." This makes a lot of sense... in fact Blaise Pascal himself trusted it to get him out of any awkward situations in which, after he died, he discovered that there in fact WAS a God.
What's kind of scary is when you reverse the logic. "If there is, in fact, a God, despite the utter lack of any rational evidence of Him - then I'm screwed, because I chose to take the path which I was created to take. If there is no God, then religion, that structure which we humans have created around the presumed existance of an irrational, pathological creator, has caused more harm than we know how to repair."