This thread bothers me deeply, and I'm not sure how to respond but feel I should. Looking at the subject from a totally different way.
I come from a background of severe negligence and abuse from my parents. Punishment was meted out in different ways. Sometimes it would be the spontaneous clip round the ear hole, soon forgotten, but my mothers favoured punishment was tying my hands together and hitting me on the back of my knees with a whippy cane, until weals rose on them. It probably stung a lot. I don't remember the pain.
However, when I'd really upset her she had greater punishments lined up - two I remember to this day. Either I'd get locked in the coal shed for a couple of hours (after always being told there were rats in there) or being locked in my bedroom for hours with no food or drink, not being let out, and when I weed myself, I'd get another punishment for that. The effects of this psychologically has stayed with me all my life.
I'm not looking for pity, what I want to say is it bothers me that, from my experience, taking away the short sharp shock treatment meted out throughout the animal kingdom throughout time may leave some parents to turn to the far more long term damaging of the premeditated punishment 'just you wait til tonight' sort of thing.
I'm not for one second suggesting that any parent should systematically hit a child but I fear if the punishment instinct is made illegal then parents may resort to other, premeditated means of punishment, which instead of lasting until self dignity is restored, will haunt for a lifetime.