That's not right. It's important for the coach to take charge of this if the parent doesn't have the self-control to leave his son the hell alone during the game. That's when dad (or mom - I've seen it) gets invited to watch the game from beyond the right field fence.
My older son's baseball team had a kid whose dad realized that he had a little self-control problem when it came to watching his boy play ball. So every game he would take his folding chair and go sit by himself to watch the game from behind the center field fence. I always appreciated that.