Why do people think that god hates gays?

I'm bi, and apparently everybody knows even though I've only told like five people. I have had people text me and say I'm going to burn in hell, blah blah blah. I am not personally a church going person, but I do not try to force people to believe what I believe. What I am wondering, is why so many people out there thinks that the bible says god hates gays. In my opinion, the only reason it says man and woman is because it takes a man and a woman to have children. I have recently got yelled and preached at because I'm bi in my best friends house. Her mother went ballistic and started saying that I should have never been born, I'm going to burn, I'm doing the devil's work, ect. It all made me think, why do people say that god hates gays? Where have they found that? Are they just using that as an excuse to cover their homophobic actions? Do they really think that?

I want some input from people that might have the slightest idea why this is happening. Please, even if you are against gays, be polite about it at least and don't judge people on only that.