Great point! And that is clearly a valid reason for why anal sex is unnatural and could never have been intended to happen, just as hymen tearing is a reason for why penetration for women is unnatural and could never have been intended to happen. As Nic has already pointed out the illegitimacy of fellatio I think all we're left with is dry humping, dogs had it right.
Homosexuality is pretty gay. No, really. I'm not coming from a point of moral superiority here, but it's pretty obvious intercourse was never meant to be same-sex
It's pretty obvious people were never meant to wear clothes.
And by the way, it's pretty obvious same-sex intercourse actually works. So what you're saying is (and I think this is pretty obvious) that the human body shouldn't do something which the human body can do because it somehow wasn't meant to be.