Why is beastiality frowned ..

Considering we as humans find it acceptable to do all kinds of other things to animals (make them live in cramped conditions on industrial farms, hunt them for entertainment, use them in experiments, kill them for food, ride them in races, exclude them from their natural environment, kill them for their skins etc etc.,

Whats wrong with using them for sex as well? (No I'm no personally interested in it.. just curious about the double standard)

If you havnt got a problem with it then go and shag a sheep