Ok it's easy a slap on the back of the legs is fairly easy to imagine, beating your child with belts,fists etc is beating a child and is totally different.

I am a child brought up in the 60s with occasional slap, could be by parents, teachers or police - all were allowed.

Soon taught me discipline and I rarely was a bad kid.
no mental hangovers from it,no recurring nightmares as I wasn't beaten up.

i totally agree with it being used in moderation