re: If Peyton Manning would whip his kids like Peterson did...

I don't think anyone would have immunity for assaulting a child. Unfortunately many societies didn't mind hitting defenseless children so its acceptable in some cultures.

I think a more interesting question is: if a promininent female was found to have assaulted a child. Would people defend her? I've seen plenty of mothers slap and assault children in public while working retail. Women's role in child violence is extremely under-discussed.