I was spanked, given the old cane, etc and hey guess what I am still naughty. It does not work for some kids, but for others its a punishment that keeps them in line.
But only for very serious "offences" that the child commits e.g. bullying another child.
From someone who was regularly disciplined by spanking as a little kid, I found that as long as they do not do it in anger, smacking and spanking are fine. If the parent is venting their own feelings instead of hoping to correct the child, then physical discipline is inappropriate and should be postponed until the parent is under control.
They can punish them in better ways.
There are better ways to discipline children than violence. They are learning every minute of every day and teaching them that violence is an option if your are bigger and stronger teaches more than just that they've been naughty.
Depends on the severity of the act, but for most acts no.