Considering, no one cared about gay men or women in history until Christian based religion dominated (see Greece, Rome, etc.) I blame religion. A lot of people aren't going to read the bible, but cherry-pick it to suit their needs. Removing pedos (the cherry-picked same sex attracted ones) from the equation (as there were a lot, especially with Spartans and Romans), and there are still LGBT people, of age.

The same bible that says gay people should be killed also says to love thy neighbor (ironic, as I am cherry-picking right now). I feel as if the only reason LGBT people are in the bible is someone had an agenda against someone they opposed, and decided to slander based on something like who they chose to slept with.