I agree that this sounds like an activist ploy. If you look on the bottom left hand corner, there is PETA -- they seem to be in on this one together.

My riding instructor used to "punch" our horses. Some of the horses were very stubborn so she'd give them a good smack or a kick to smarten them up or get them going. It's a huge animal, it's not like it's getting hurt. Accidents happen -- Get a that many horses together and something is bound to go wrong eventually.