Well, the father were clearly in emotional rage when he tore that 18yo apart. I will argue if you are NOT in emotional rage in that situation you are doing paranting wrong. If he were to have the good sense to think "lets pacify him, but not go overboard and knock him out", he would in fact not be emotionally involved and hence, doing it wrong.
I woulda killed that dude looking him in the eyes.
+ you'd be taking one for the team! Sure you'd get a jail sentence, but we also know that that dude will be out on the streets again within a year, doing it again.