BTW, above I was responding to comments by Justbaseball, etc.
As to the original post, if I were the principal of that guy's school, I would want to know that this coach is giving our school a bad reputation.
No, he's not risking injury to anyone, but he is a bad role model for kids, and leaving him in a position of authority suggests that his superiors endorse his example.
So I think you should consider reporting him, unless it puts your son at risk of retaliation from the coach.