As a degenerate father with a kid who skis, I will say that dad is a fucking dumbass who should be smoked in the face with a skateboard. I bet he wouldn't have hit the guy if he was a 40 year old racer in lycra. With a temper like that, dude is prolly just weekend dad anyways.
Not saying the boarder wasn't an awful rider who didn't know how to cruise through a busy run. If that would have been my kid, I would have checked on him, checked to see that the other CHILD was OK, and then punk the shit out of him with words and make him feel really stupid in front of his friends.