Every and each one of the gentlest colts known to humanity are bound to try and kick at least once in their lives. It is a normal learning curve of a growing horse, and a normal part of their communication. Although I seriously doubt that he is now mimicking your friend (give his intelligence some respect - he is well aware that your friend is not a horse!), you won't really benefit from trying to find a set reason for why he is kicking as such. Even if you're right, it doesn't mean anything anymore. Put it plain and simple, he just kicks. What is more, he is not a kicker - this behavior is not something that defines him, but just something he uses to express himself. It is nothing negative, it's just something many horses sometimes do.
Instead, treat every time he kicks separately, trying to understand the reasons behind the exact case, and not as something you have to re-train, but just as a normal, neutral part of your training. He is obviously testing his limits and showing a huge amount of disrespect towards his handler - and, if it happens while you're working with him, maybe it is worth considering if something in your body language, timing and precision actually provokes it! Good luck.
What else came to my mind - if he kicked just when your friend barged in his space, expecting him to move, I'd fully understand a kick from the horse, as he has no obligations to respect somebodies' space if they don't respect his and treat him without any feel, timing and common sense. It's just as if a person hit a horse in the face without a warning a reason, and then got all upset because the horse bit them in self defense.
Then again, there is a way to teach a horse to kick. Put some kind of intense pressure on him and then release it & back out of the situation as soon as he kicks. The horse will learn that a kick takes away the pressure and will acquire it as a "correct" behavior. What has been your reaction to the times you've observed him kicking?
I have come a long way, to surrender my shadow to the shadow of my horse.
Last edited by Saranda; 03-20-2014 at 03:50 AM.