Perhaps to add to my story I'll give you a little back info on where I'm from. This was a tiny town population of about 11 000 people. Kids who live in this town don't have much in the way of entertainment, and get bored very easily. There have been problems with spray painting, broken store windows, plants in the downtown area dumped and destroyed, the list goes on and on. And it seems the town keeps coming up with excuses, "they're just young" "they'll learn" etc etc. And as they're so young and so many it's hard for the police to really do a whole lot to stop them. We had the front window of our dojo smashed a few months before this happened, plus someone had tossed paintballs at our building which was not fun to clean off I don't mind telling you.
Was my Sensei wrong in how he reacted, yes for sure (though he could claim self defence as I stated the kid did take a swing at him)
Was he maybe just trying to make a stand and show the kids that they couldn't just get away with whatever they wanted...? I'll leave it up all of you to decide.