Laws of nature. Name one species of plant or animal on the planet earth that's naturally homosexual. There isn't any.
Only those born with a disability or mutation would engage in such an unnatural behavior. Nature usually eliminates them to ensure the survival of the species, as it's doing now through AIDs and various homosexual diseases and infections. Homosexuality is unnatural in every aspect. Culturally, naturally, spiritually. No where is it considered "normal" but in the irrational mind of the homosexual itself.