I guess for many of the staunch believers it's like having sex with an unprotected soul. Perhaps it is not really so much about their god/s but their divine insurance policy. I remember once living with a born again Christian who even wanted a child with me.
I was very skeptical about her religious zeal, but totally flummoxed by her contradictions. She had a bible in very corner of every room in her cottage and a stash of dope behind every bible. She did all sorts of things that seems utterly incompatible with her "belief" including having 2 abortions.

I ask the same question: So what if other people believe differently? I don't get all up in arms because some people believe in gods, so why should they get freaked out by people who don't share their beliefs? Is there some need for validation of their beliefs or something?

It unnerves them..