WOW, I forgot the hebrew name for those people, but I know the english word for them is Zelots, they are the same people in RMS spitting at an 8 year old girl and in Meir Sharim terrorizing shopkeepers not to sell english books.
I wonder if your older son met such a person and was turned off and didnt tell you.
BTW if It was my kid, and the Rav wouldnt do anything, id call the Police.
One it will make your kid respect you and realize he is a criminal and not a chashov a yid , and its illegal to touch anyones kid thats not your own, Perhaps a few days in Jail and a punishment will make that clear.