Homosexuality is not a threat to marriage (Lewis Black makes it hilariously clear), though it is a threat to the homosexual’s own marriage to a woman, ha ha.
But the ideology of homosexualism, so to speak, is a threat. This ideology argues that sodomy and promiscuity are physically healthy, that sexual attraction to same sex is spiritually healthy, that gay effeminacy does not turn men into contemptible weaklings, that crazed lust substitutes for love, as well as that two gays can adopt children with happy consequences for all concerned. Society will be harmed if this ideology is taken seriously.
Ass-fucking is a choice. Sexual attraction to same sex, if it is a choice, is vicious; if it is inborn, then it is, though not wrongful, a chronic spiritual illness. There are many mentally ill persons who refuse even to acknowledge that they are ill. This makes their condition so much worse. Same for the gays. The more resolutely they believe that they are perfectly OK, the more corrupt they become. It is true that no definitive cure for homosexuality has been found. Well, neither has a cure been found for alcoholism. So what? That does not mean drunkards are either holy or happy. Besides, that only makes the Catholic solution of “chaste friendships” for gays more relevant.