After all, the heart wants what the heart wants. And is the practice of bestiality really all that harmful?
Think of it this way: raising sentient mammals so that we can eat them is considered perfectly acceptable. So which fate would you rather suffer: having your head chopped off so you can be eaten, or being screwed occasionally by a horny human?
But, I could be wrong about that; maybe some men actually do prefer other species to their own. And if they do prefer other species, who's to condemn that practice -- or at least desire -- as morally repugnant? Certainly not meat-eaters.
The phrase "consenting adults" comes to mind. But bear in mind, eating meat hardly implies consent.
I know some readers will think I've gone off the deep end with this line of argument. In fact, my sensibilities are not so different from yours: I agree that the "ick factor" here is huge. But if we're going to allow the ick factor to dictate the legality of various activities, we might as well outlaw homosexuality since so many people find the idea of that revolting.
Let me emphasize, I'm neither condoning nor trying to normalize any of these practices. And I don't think homosexuality should be outlawed. I just want to point out that if one of your guiding principles is that you don't choose your own sexuality, then, well, you should stay principled.
Drawing the line right outside your own perversion and disapproving of of others is, well, discriminatory.
[Here's another way to look at it. You've probably heard of dolphins which have gotten sexually aggressive with humans. And most of us have witnessed dogs trying to hump someone's leg. When we see this, we tend to find it funny. (Though with dolphins, it can be dangerous.)
We never react by thinking, oh, that is a really perverted dolphin! Nor do we ever think, what a grotesque, sick dog -- we should put it in jail! Most of us just find it sort of cute and almost endearing.
After all, they're just dumb animals whose sex drive got the better of them.
It's easy to lose sight of the fact that humans are just animals, too.