I think if he reacts in that manner to having a horn sounded at him, then he certainly has issues that need addressed before he does assault someone.
But if I were the cyclist, unless he is prepared to stand his ground then he needs to ditch the horn. So tired of seeing cyclists with cameras and horns, who when confronted by motorists run away. Have the balls to get off your bike and stand your ground, none of this nambi pambi using your bike as a shield. If your going to blare your horn, wave your hands about and shout, then be prepared for confrontation. I'm not advocating 'getting the first punch in' but I would be certainly defending myself and not running away.