I am 100% against it lmao. How on Earth are we meant to teach children violence is not the answer (minus self defence, but that's a different matter) if we allow them to be smacked themselves? There are many different ways and as an odd example using the show Supernanny or w.e with Jo Frost, she didn't used to smack kids to teach them a lesson - at most she would pick them up and carry them which is not smacking.
It's never ever ever ever the answer and I know a **** tonne of people (myself included) who have suffered horrifically emotionally because of the amount of times our parents have smacked us (and done A LOT worse...) as a child when they simply didn't need to.