There is an awful case in Washington of a man killed during sexual congress with a horse. Apparently, this occurred at a farm known among those who engage in that sort of thing for permitting animals to be used as sexual objects, and yes, unfortunately, video taping is involved. I only mention it because there is actually a bit of resistance
to passing a law making bestiality illegal in Washington. Also, the reasons some give in support of such a law include, "animals can't consent to sex," and "it is animal abuse." Both are true, of course, and are sufficient rationales to support outlawing bestiality (as most states already do). But at the most profound level, they are inadequate rationales for the ultimate reason why bestiality is so very wrong.
Peter Singer, the Princeton bioethicist and father of the animal liberation movement, has notoriously written that there is nothing intrinsically wrong with bestiality since, when an animal and a human copulate, it is just two animals rubbing body parts. This is where I believe the true nub of the issue is to be found. Singer is an adamant foe of human exceptionalism and nothing would demonstrate our unexceptionalism
more than countenancing human/animal sex. Thus, it is at this philosophical nexus, even more than the animal abuse angle, that I believe most urgently requires an unequivocal societal condemnation through law of bestiality.
As unpleasant as this topic is, I am gathering my thoughts on the matter and plan to write more extensively on the subject. Yuck.