How do you live with yourself after either:
1. taking your anger and frustration out on your child using physical violence or,
2. calmly and coolly using violence to subdue your child's will and thereby proving to him or her that the one who's big and strong is allowed to physically subdue the one who is smaller and weaker.
Not only has pain been shown to only be a short term deterrent, there are hundreds of other philosophies and tools for either discipline or no discipline out there that are more successful.
You can absolutely find a way that not only works for you, but works BETTER than any spanking ever can.
I admit, I get extremely angry when I see people supporting corporal punishment, especially in South Africa, and I know the parents who do this are mostly ( I say MOSTLY)
The same ones who do not advocate car seats, who do not spend enough time with their children, who don't get actively involved in their school lives, who probably still live by the word of the Bible as if it is the only book ever written, and does not question anything that they learned via tradition.
Who probably drink and party on weekends, are not too concerned about drinking and driving. Thinks all "insert race of choice" people are beneath them. In short are caught up in so much irrationality, that no matter how much evidence you present to show them that corporal punishment HARMS your child in the long term they will find a way to justify to themselves that it's okay, because they were spanked and they turned out okay.