[concerned about politics]

Well, here's the difference on three out of four of those categories you mention: children, animals and dead people cannot give consent and therefore we do not allow people to have sex with them.

Using your logic:

What do you mean you "don't allow?" Why not? There are no absolutes, remember? No right or wrong?
I thought you were supporting the strange. Dead people are dead. If your logic is correct, why not do them? They don't care!
Animals can't speak, so how do you know? Maybe the beastialite feels they are saying yes. Who are you to question them? What gives you the right to judge them?
Children? Talk to NAMBLA about that, According to them, their victims did approve.
Gee, anything above the temperature of liquid nitrogen is fair game. Just stick it in. If it feels good - do it!