If the kid was mine, I'd applaud the coach for disciplining my child... then I would re-enforce the discipline by:
1) Sitting him for a game (I'm sure LL would agree to this punishment)
2) Making sure he apologized in person to the coach and his teammates for his remark/ behavior.

And to answer Garths question (again), "Is it appropriate for a grown man to slap a child of 12 across the face?"

Yes, in this instance it is. You see Garth, I think you're trying to make this a black/white issue. It's just not that simple. If the kid ignored a sign given by the coach, a slap is not in order. But sometimes physical contact is used (and rightly so) to put a kid in his/her place.

BTW- The coach is retired from the NYPD, so I'll bet he's seen his share of violence as well.

Yes, it is that simple. I've spent years working on issues such as this. I've seen the studies, the kids, the adults.

Corporal punishment is called for at times. No disagreement. But it is never appropriate for a grown man to slap a child across the face. Period. The lesson intended is never the lesson learned.

There are places better designed for corporal punishment and offenses that call for it.

And yes, I know the coach is a former police officer. He should be ashamed. If he were on duty and witnessed that, he would be obligated to intervene.