I don’t know whether spanking can be called child abuse or not; but setting that issue aside, I’m pretty sure it just doesn’t work as a method of discipline, and it’s old-fashioned and unnecessary as well as ineffective.
It’s problematic because some kids have a higher threshhold to pain than others and if they have a stubborn personality they will probably simply take the pain of a spanking rather than back down. What do you do with those kids? The only answer would be spank them harder, until you find a level of pain that has an effect on them. This really could bleed into (pun unintentional) real child abuse at some point. And what do you do if you never find that level? There’s no answer.
It also sends a message to the child that it’s okay to use violence to solve problems. And furthermore I’m convinced it makes the adult lose control of a discipline situation because it will inflame his own emotions, inevitably. The more you lose your cool in such a situation, the less power you actually have over your child’s behavior (and the more they sense that and use it to your disadvantage).
I used to be fairly lenient about spanking and thought it could be okay if used sparingly. Now that I have children of my own and have to control their behavior on a daily basis I don’t see any use for it whatsoever. Plus if I had to physically hurt my children to get them to do what I wanted, I’m pretty sure I would have mixed feelings of guilt and shame after it was all over and done.