It's all about being needy.

The reason behind all of the bigotry - behind all of the devout Bible thumping - is to elevate one's position within the universe. If God loves you more than he loves me, that clearly makes you a superior person in your own eyes. If you can somehow brand me as a deviant, it makes you appear to be the better person in your own mind. It is, in fact, all about the ego.