The report here says that the match was already stopped and that the kid just didn't get off the exact split second the whistle blew (as usually happens).
Either way, a man attacks child, and people are glad no one stopped the man. That's what it has come down to I guess. I would not have stood there and tolerated that.
Arm in bad position or not, what that guy did should be criminally prosecuted. Don't listen to his lawyer for even a second.