This was mentioned by Jess in the comments, but I think it deserves its own post. Apparently polygamist sect leaders are upset that Santorum lumped them in with homosexuals and adulterers. After all, you can't cheat on your wife if your mistress is your wife too!

Frankly, as a libertarian who want so do everything possible to crush the sanctity of the family, I think all of the things Santorum mentioned in his little laundry list of threats to the American family should be totally legal. I have no moral problem with polygamy. If you want to marry more than one person, and all parties are fine with it, then great! Knock yourself out, just don't be surprised when it doesn't really work out the way you intended. Adultery is currenlty legal, but needs to be controlled. Essentially, if you can get a signed statement from your spouse that it's okay for you to sleep with other people, then by all means, have at it. If no statement is forthcoming, it should be prosecuted as a breach of contract. Or maybe you could set up a J-Lo style cheating charge account where you have to pay your spouse X amount of dollars for every other person you hump.

I have no problem with incest being legalized. Again, if you and your sibling both really want to go at it, then hell, I'm certainly not going to jump in and stop you. Just don't be surprised if everyone thinks you are fucking disgusting and shuns you forever. Bestiality should also be completely legalized, as long as total consent can be established from both parties, via testimony or a written statement.

However, I do feel that old people should be legally forbidden from even ever getting naked, because that is just grody.