i dunno. When i was growing up i got slapped, a lot did. A few got worse.
Thirty years ago the following would not be unheard of:
Two blokes in a pub. Bloke 1 says " I got home from a hard days work on Wed and do you know what? the missus hadn't even got my dinner ready" Bloke 2 nods, sympathetically. Bloke 1 continues "It happened again on Fri, now I'm a patient man but i had to give her a bit of a slap. How else is she going to learn?"
^ We frown on this now yet at the time it was 'oh it's between a man and his wife, let them deal with it' 'keep it in the family'
Not saying this kind of thing doesn't happen any more. It does. But it is no longer a typical conversation in a pub. It's no longer acceptable.
The day is coming when striking children no matter how 'lovingly' (eh?) will be seen as unacceptable too.