I do wonder about the mental well-being of a generation of children brought up with the stigma of being put on a naughty step or being put in isolationshut in their bedroom; mental punishment may be as damaging as physical punishment. Physical punishment may take other forms, not just slapping eg restraint, holding still to admonish a verbal assaulttelling-off, etc..
If a child is being punished, they need to understand why. It’s no good to just slap them, it’s no good to just scream at them.
A lot of parents need to just step back for a moment and consider why they are punishing a child – unfortunately it is more often because of their own frustrations, lack of time for the child, selfishness or even embarrassment rather than anything the child has actually done wrong.
A gentle slap in the right circumstances with a considered explanation of why does no harm IME; lashing out in anger just does harm and is wrong.
Just my thoughts.