I can't even understand Religion being a factor, as In the section of the bible it says man may not sleep by man, it also says Mixed fabrics = death by stoning. So why pick and choose?
I'd say it's more of a mental thing, in the sense that as long as it's not allowed, they can pretend that homosexuals don't exist, similar to how the "war on drugs" works. We pretend that as long as their illegal, everything will be fine and that drugs don't exist. Yet the reality is that they do, and we'd be much better facing up to the issue, as oppose to living in a fairy tale land.
Because people are scared to fucking death of change. During the renaissance so many people were afraid of what was to come. Also people are just close minded shit heads.
"Marriage is not between a man and a woman, but between a Love and a Love." -Frank Ocean