Yeah, it's a bit of a stretch to defend the general proposition that if we've always done it that way, it must be good. If it were the topic of the OP, I might be inclined to try to defend the general proposition that if we've always done it that way, it must serve a purpose, but then I might find myself in a situation where I'm defending religious intolerance, and I really don't want to do that.
So, my point was that this is the norm, an awful lot of us experienced it, and didn't think we were harmed. It's hard to grasp that if it were such an awful thing, even many of the "victims" would say that it's a good idea.
After having children of my own, there has been only one thing that I can think of that has changed dramatically from my preconceived notions about how children "ought" to be raised. I have gained a thorough appreciation of the full implications of the fact that children don't have an "off" switch. It's all very easy to sit back and say what ought to be done in any given situation, but there are times when parents really have stuff that has to get done and they have a child who thinks that it is far more important that the parent follow the child's agenda, instead of vice-versa. In those circumstances, if the worst thing that happens to the child is that it experiences a certain degree of temporary pain and/or fear, I'm not going to call someone a bad parent, even if I think there was a better way to handle the situation. It would be all very well to talk about what a perfect person would do given an optimal situation and plenty of time to deal with the circumstances. Sadly, parents don't have time to call a committee meeting of child care experts to discuss how best to get Johnny to school on time. Sometimes, a threat of pain might be the best you can think of, and the threat will not be effective unless it is occasionally carried out.