Recent bestiality cases
http://seattletimes.nwsource.com/html/localnews/2002389068_brodeur19m.html
Having some experience in this area, my question is not Why? Rather, it's What's all the fuss about? People are way too squicked about this.
About this case specifically: the horse in question was mounting the man. It seems more like human abuse than animal abuse.
We don't need bestiality laws, we need animal abuse laws. Oh, we already have those? They're redundant. Bestiality laws are written with the excuse that we need to protect animals from harm and abuse. Wait a second, we already have laws for that sort of thing. If you can't prove harm, then what are you prosecuting?
I know what they're prosecuting: stuff they find disgusting, and stuff the bible says is bad. Disgusting, by itself, still isn't illegal, just like the stuff that the Bible says is bad isn't necessarily illegal. These aren't good reasons to make laws, and we should shoot 'em down.
Plenty of people want to have sexual contact with a stallion, and there are a few reasons I can think of. Their genitals are novelty sized, which turns some people on. They're beautiful animals, usually sleek and muscular, with short, soft, and shiny hair. More generally, it's a good feeling to satisfy someone else's sexual needs, to provide them that release, and quite an exotic experience to satisfy another species.
And what about this notion that animals can't consent? You can force them to do things, sure, but they can fight. If an animal is too scared to fight, there's probably been some abuse going on. You just can't intimidate an animal without physical violence, and that's illegal. Just think about it: you can't give a cat a bath, let alone stick your sensitive flesh where the cat doesn't want it. And you can't say to the cat, Don't move or you're dead!, because the cat won't understand.
If a dog starts humping your leg and you let him finish, is that lewd? Hmm....