Very interesting discussion - and my sympathies lisalisa, that sounds hard.
I just wanted to say that unlike some posters here, I was smacked by my parents and have absolutely no bad memories or resentment about it.
It was an extremely rare occurrence and was reserved for situations where we were doing something actually dangerous (rather than just naughty). It was the ultimate sanction. It didn't hurt - my sisters and I hit each other far harder than that - it was simply a signal that we had done something absolutely beyond the pale.
For "normal" day-to-day transgessions we were reasoned with or had time out. We had very calm parents who never lost their tempers and I had a very loving and secure childhood.
I think that in many other families smacking is or was a very different thing, part of a deeper pattern of abuse or lack of control. So it's easy for me to see that another person might have a very different feeling about being smacked. I just don't think it was the smacking "per se" that was the problem.
I don't buy the theory of "it's not acceptable for an adult to use physical force with a child because it wouldn't be acceptable for another adult" because we all the time treat our children in ways which would be abusive if applied to another adult. If your dp shut you in your room or witheld treats or decided what time you had to go to sleep or what you could watch on TV or any of the millions of other ways in which we control our children's lives, it would be abuse. But these things are acceptable precisely because we are adults and our children are children. The rules are different. That doesn't make smacking right, but it does mean you can't invoke that as a reason for smacking being wrong.
I have no intention of smacking my children. My reason is that although I would hope to be as careful and judicious as my parents, it's too easy for children to copy this behaviour indiscriminately when dealing with other children, and they need to learn better ways of resolving disputes.
Phew, have written an essay. sorry!