People often support liberal views on sexual behavior by saying that whatever two people consent to do together is ok. Theodore Dalrymple has evaluated the case of German cannibal Armin Meiwes, according to this principle. Unsurprisingly, this principle gives no reason to oppose Meiwes's seemed to guide the sodomy ruling last summerbehavior, since his victim had responded to an internet ad asking for "a young, well-built man who wants to be eaten". So if there's something wrong with this, then that principle is in need of work.
Of course, some people revise the principle: sexual behavior is wrong only if it's non-consensual or if it harms someone. Some may try to argue that having your sexual organ cut off and sharing a meal of it with the person who cut it off, who then proceeds to kill you, does not harm you if you wanted it to happen. I have trouble understanding such a move. People can certainly want things that harm them, so wanting it doesn't make it not harmful. The less liberal principle to guide liberal sexual morality thus is able to handle this case (or one like enough to it if it turns out that this wasn't truly consensual in all the details). The more liberal one that does not.