Personally for me, I wouldn't care if it was my horse or a horse I have in for training, if it corners me and wants to kick, it's gonna get a come to Jesus meeting, and learn some manners. That does not mean I'm going to be abusive to the horse. It simply means he's going to learn who the boss is and where his place in the line up is. To me this is a horse who wants to be boss, and that is out of the question. Tip toeing around the problem trying to figure out why, is not going to fix it. The behavior is going to get much worse.