It would have felt great for a second to slap that fool but you probably would have regretted it the next day. No telling how that would have been received by other parents. Now he is the bad guy.
Grabbing a kid in a high emotional situation is never a good idea, in any situation really.
Was the Coach impaired?
Alcohol in the dugout is not a good coaching decision to be sure.
Save those kind of refreshments to after the tournament.