1) Oh, look! Another witless idiot who thinks everything he doesn't like can be scoured away by a continual program of violence.
2) Homosexuality exists across the animal kingdom. We're animals, too. (And why the hell should anyone care if gays want to marry one another? Let them. They can't do any worse by the institution than straight people have. Have you taken a gander at the divorce rates lately?)
3) Even if homosexuality were a choice, so is religion - so unless you like the idea of having your religious freedom taken away because you chose it (as opposed to its having been in-born), then you might want to reconsider your stance. Remember: Everything you do - everything you advocate for others - will eventually make its way back to you. And in your case, because you can’t be bothered to follow the Golden Rule, your own policies will be back around to bite you in the ass.
4) Criminal gene? It's a delicate mixture of genetics - and not just one gene, but multiple genes working in consort - that help to form the individual. If "criminal genes" - and exactly how does one define a criminal anyway: As a person who breaks civil and criminal laws? Or are political dissents and homosexuals included as well? - are ever found to exist, that would in no way guarantee the person carrying them is going to become a criminal. Genetics! How the fuck does it work?
But one thing is certain: If the potential criminal - cursed by "bad genes" or merely raised in a bad environment - were to grow up in a violent household where punishment is dealt out with the belt and where non-violent coping strategies are never taught, that might be just the stimulus required to push him over the deep end.
So congrats, dipshit; you fail on every possible level.