Black, seems like we're on the same page with a lot of things.
Stepping in is a dangerous path to go down. As you stated, it depends on a LOT of things and who are we to judge?
This brings to mind a US father who was up here visiting and was out shopping with the family. His son (3 I think? still in diapers anyways) was being a total brat in the parking lot and he gave him a little swat on the padded ass, he was reported and arrested and had to come up here to face charges.
I actually remember reading about the follow up and after posting bail, coming back up for the trial, the case was reduced to (something a LOT less than child abuse) and he was let go with time served. For once the newspapers reported ALL the facts and even though there were witnesses that stated it was just one light swat in the diaper clad backside, the police were forced to charge him.
Now I was one who was hit with everything from wire coat hangers, tree switches, wooden spoons, backhands across the face, I don't advocate using any "impliment" but a total hands off approach isn't the way to go either.
One benefit however is that I did learn how to take a punch......