well, true believers in anything can be hard to deal with. You just have to put yourself in their shoes. Imagine that you truly truly truly believed that you had found the one real path to happiness, salvation, cure, freedom whatever....

Wouldn't you want to share that with someone? Wouldn't you want to use that help other people?

IMO, that essential altruistic theme is what gets so distorted both by the believer and the "non-believer" who is often the target.

"The mistake we make is to attribute to religions the errors and fanaticism of human beings."
Tahar Ben Jelloun