In that case the father did something violent directly to his son’s teacher (rebbe) in front of the other classmates. That fact may make a difference. It isn’t a case where the father robbed the shul’s pushka and the school expelled the son. It says the son is welcome back once the father apologizes.
Regarding that Austrian guy, he isn’t NK but he’s stam a meshugana. And he didn’t hurt the community. He used his children as pawns. Trying to enroll his boys in a girls beis yaakov and suing the yeshivas for not teaching Austrian studies.