I know that upholding idealism can be hard in the face of practical reality, but I'm hoping I won't smack my kids when/if I have them.
Still, I'd say the very popular idea that kids will get unruly and impossible without corporal punishment is just a myth. Such punishment is just a tool in a parent's toolbag. Some parents use other tools.
edit :
Corporal punishment also runs in families. Smacking passes on the tool. Maybe somewhere down the family line, it will cause harm even if your own punishment didn't.