lolMost of them don't actually think that they're spreading lies. The road to Hell is paved with good intentions.
Edit: What a terrible analogy to use when my purpose was to bash religion.
And you have a point. I can perfectly understand why a Christian would want to convert people to Christianity. When a Christian sees nice people or people he knows and cares about who are not Christian, he is filled with sadness because he knows they are going to hell, and he doesn't want that. So he will attempt to convert them. It sounds good to them, but they do not realize that people do not want to convert and are just annoyed by it.
Also, I apologize for my excessive use of he/she. If I think of a better way to word that I will change it.
Edit: Fixed