I'm not judging you Erin, but I just find that it's harsh and that there are better ways out there to discipline a horse rather than kicking.
You can do whatever you want, but I'm just expressing my opinion.
I still don't see any situation that kicking a horse would be acceptable.
I have seen people kick a horse in its belly because it wouldn't stand still. I've seen someone kick a horse in its belly because he wouldn't move over. I feel that there are better ways to get what you want than kicking.
I do however, think, that if you put you leg up and the horse walked INTO it, is acceptable, because the human is not exerting any force, and the horse makes the mistake of walking into it.