The greatest single cause of
atheism in the world today is
Christians, who
acknowledge Jesus with their lips, and walk out the door, and deny him with their life style.
That is what an unbelieving world simply finds unbelievable.
Wow! This node seems to have worked out well. For those who care, I got the contents of this node from the beginning of the dc Talk song, What if I stumble?, where there is a voice over which says these words.
On the other hand, I think I must disagree with some statements below. Reason (or rational thought in any of its various forms) is not incompatible with Christianity, any less than it is incompatible with being agnostic, atheistic, etc. Some of the most rational people I know are Christians.
In any case, I'd advise anyone who has had bad interactions with Christianity is this. First, learn what a Christian ought to be. Then, bear in mind that one major premise of Christianity is that everyone has failings and problems - and that they don't go away when you get converted. Jesus didn't hang out with good people. I'd advise you to read CS Lewis' book, the Screwtape Letters, for an excellent explanation of some of Satan's methodologies.