I know some might find this harsh, but it is an easy, simple way to keep a horse from kicking. I have started plenty of colts, fixed a lot of problem horses and I take an old-school approach to training horses. Sounds like your horse has a bad disrespect problem. I would get a cotton rope, make a loop on one end with a hard knot and carefully loop it around one of his back feet, just above the hoof. Only use a very soft, larger diameter cotton rope to avoid burns! Take the other end of the rope, run it up between his front legs and through the halter. Don't tie it so tight his head is tied down, but don't leave slack in the rope so he can get tangled. Do this in a round pen or a small corral. Then proceed to try and climb on his or approach him in a way that made him kick before. When he kicks out, he will learn that his head will be yanked down rather uncomfortably and therefor will teach himself a lesson. Hope this helps!!