You've never dealt with an animal that thinks it can dominate you, have you? I have - not cows, but goats and horses, and there is no doubt about it, when that animal decides to push you around, it absolutely WILL hurt you if you don't let it have its way. I am well versed in animal body language and I know the difference between fear and a challenge.
If livestock were left entirely on their own, with no human coming within a half mile of them, then there would be no opportunity for them to hurt people, either intentionally or otherwise. But that isn't going to happen, so they must understand that the humans that are in their world outrank them. I am as kind as they allow me to be, but I will not stay out of my pasture because a miniature horse thinks it owns it. Selling such an animal relieves me from having to deal the problem, but it doesn't relieve me of the responsibility if a child gets killed by the "cute little pony" somewhere down the line. A "come to Jesus" moment like
@Dona Worry describes is ugly to watch and unpleasant to be in, but it can be the difference between a very short life for a dangerous animal (horses get slaughtered too, you know) and a much longer, productive (and potentially pleasant) life for an animal that has learned that it isn't at the top of the pecking order.