Why do people think it's okay to be so mean and unaccepting to gay people?

I know about the Bible passages, I've read them and researched them and it says it's likely due to mistranslation that homosexuality got the "abomination" treatment. But even if homosexuality is a sin in Christianity, why do people think they have the right to increase the suffering of any member of the human race? Jesus says "love your neighbor." So why do people think they can do horrible things to gay people? If God says "leave judgment to me," then isn't judging putting oneself equal to God?