Idiotic on multiple levels:
1) What does that teach the child? "Don't do something because I'm going to get hit". It should be about "Don't do something because it is WRONG".
2) You trust EVERY PARENT just because they are a parent? What if the parent is a complete psychopath? They have the right to hit their kid just because they procreated?
3) Ground the kid. Take away their electronics. How about TALK to the kid? (unless the parent is a complete imbecile and doesn't know how to mold their own child with his/her words or example).
Resorting to force against a small child is done because of the absence of a working brain.
In no way do I support lack of discipline. My kids get away with NOTHING. They know that if they step out of line they are going to lose something they want. If that doesn't do it, they know that dad is going to embarrass them by showing off my cool dance moves in front of their friends.
I never have to lay a hand on them.