Where in the Bible...?

does it say anything about killing gay people? Why do so many Christians (who are supposed to forgive and forget) think being gay is a sin? It's nowhere in any Bible I've ever read so I'm just curious. I have no religious affiliation, I'm just tired of seeing people being murdered because of a difference in ual orientation. If it's a difference they're being killed over, how can these killers even claim to be Christians? How long until religious people finally widen their minds and stop hating because of trivial differences?