“I don’t care how much a bully is bullying your son.”
Remove this statement from your post and you have a reasonable point. Keep this statement in and you convey the message that no matter the form, no matter the torment, no matter the brutality, you think a parent should not intervene.
I cannot do that, and did not do that when my son was relentlessly being bullied by two thugs. . .thugs that only stopped when I made it clear to the thugs that they would do nothing but hurt the rest of their life if they continued. Scared them straight. I did what the school refused (or was unable to do), and what the parents could not stop.
Physical assault is physical assault.
Is there anything to go on to suggest the underage victim of this assault by an adult committed any physical assault on his son? Not even the testimony of the nutbag father, from what I have seen.
If you have a socially or physically weak child, hovering over them like a helicopter gunship is NOT going to do them any favors. In fact it is behavior like this from parents that I see most often being the cause of them having a socially and/or physically weak child.