I teach all my pitchers to have short memories. Obviously remember the mistake you make so we can work at it so you don't make it again, but when it's crushed like that, you too your hat to your opponent and get him next time.
I coach kids that are this age and if you don't want someone flipping their bat and admiring their HR, then execute your pitch better. God forbid you gave the kid who hit it credit for a picture perfect swing. The batters mechanics of his swing are way advanced.
If any of the kids I coach give up a HR then "paste their ribcage" with a pitch, then they are immediately taken out of the game. This is one of the rules I state st the beginning of the season.
So, what happens when it's your son that, in the heat of competition, is proud of himself and flips his bat. Does he deserve to get hit in the ribs on the next pitch?