This says it perfectly!
"You believe that the Bible is the word of God, that Jesus is the Son of God, and that only those who place their faith in Jesus will find salvation after death. As a Christian, you believe these propositions not because they make you feel good, but because you think they are true. Before I point out some of the problems with these beliefs, I would like to acknowledge that there are many points on which you and I agree. We agree, for instance, that if one of us is right, the other is wrong. The Bible is either the word of God, or it isn't. Either Jesus offers humanity the one, true path to salvation (John 14:6), or he does not. We agree that to be a true Christian is to believe that all other faiths are mistaken, and profoundly so. If Christianity is correct, and I persist in my unbelief, I should expect to suffer the torments of hell.
Worse still, I have persuaded others, and many close to me, to reject the very idea of God. They too will languish in "eternal fire" (Matthew 25:41). If the basic doctrine of Christianity is correct, I have misused my life in the worst conceivable way. I admit this without a single caveat.
The fact that my continuous and public rejection of Christianity does not worry me in the least should suggest to you just how inadequate I think your reasons for being a Christian are."
--Excerpt from Letter To A Christian Nation by Sam Harris