I read once that there is no gay gene. Any combination of genes can result in homosexuality. We just don’t know what the combinations are. That’s why homosexuality persists and thrives even if gays don’t reproduce.
I think it’s also psychological. Sex for reproduction and raw sexual attraction is one thing; but one can have an affinity for one’s same sex without sexual desires. There also are as many gay types as there are straight types. They maybe your neighbors, friends, relatives, coworkers, politicians or religious leaders.
Sex is so taboo in our society that we’re afraid to talk about it. It’s a natural part of life so what’s the big deal? I’m hetero but I have had gay sex. Intimacy between two individuals is satisfying on many levels. It’s nothing to be ashamed of. There, I said it.
So long as people are responsible and productive, they should all be treated fairly and equally.