Smacking is not my parenting choice. My sister smacked her child occasionally when she was younger - that was her parenting choice. My boys are turning out wonderful, my niece is turning out wonderful! I respect my sister's right to discipline her child in the way she sees fit, and she is the same with me. And I understand that it is also important to understand the difference between controlled smacking in consistant discipline and hitting in anger or beating your child.
However, I feel that smacking would tell my child that it is ok to smack. To a young child, the parent is 'God', what you do is what should be done. Through smacking as a form of discipline - 'no you don't do that, that is naughty' a parent teaches their child that you hit people when you are cross with them, or they are doing something you don't like.
So then the child goes and hits someone else, after all, how can it be wrong, Mummy does it. At which the parent goes 'hitting is naughty' . Cue very confused child who has just had first lesson in do as I say, not as I do. Just like yelling at them 'BE QUIET' at the top of your voice!!
Also, the trust a child has in its parents is awesome. I personally feel that to hit my child is a betrayal of that trust. I am the person whose job it is to protect, I find that conflicts with the idea of physical punishment.
I was hit as a kid as discipline, not beaten, you understand, but I always flinched when my dad made a sudden move. He could be sitting on the sofa and suddenly raise his arm, maybe to stretch or something, and I would recoil. I do not want to see my kids flinch from me, it would break my heart.
I also don't think that smacking is any more effective than other forms of discipline. If it was, then you would only have to smack once and thereafter the threat would be enough! That is not the case, so smacking is not a better alternative. So if it is not better, why not use other methods that are not violent.
Some people say that there are some situations that you do not have time to use other forms of discipline, like what? I can't think of anything where you don't have time to do anything other than smack. If they are in physical danger then if you can get to them in time to hit them, you can get to them in time to pull them away. Voila, no longer in immediate danger and time for other methods!
So I guess it comes down, really simply, to those who think it helps and those who don't!