I remember a very long time ago, a friend of mine shared a meme denouncing the practice of smacking children. It was a flow chart, asking one simple question: Can the child understand reason? If the answer is yes, then you can use reason to dissuade the child from further misbehaviour, and so you should not hit them. If the answer is no, then they are not reasonable enough to understand why you're hitting them, they learn nothing, they're just scared and confused, and so you should not hit them. Conclusion: Never hit a child. And I just remember thinking to myself, you are basically saying that a dog is more reasonable than a child!
Now, obviously, in the case of a newborn etc., this is the case, but last I checked, even the smartest dog is less intelligent than a 5 year old. Most dogs don't even reach that level. Now, can I reason my dog out of bad behaviour? Of course not! He's a dog! He can't understand my language, much less my thought process. But can he understand which behaviours invoke which responses? Sure. He's smart enough to know if he pees in the wrong place, gets aggressive with the cat, chews something that hasn't been given to him etc., he gets a slapped bottom. If, by contrast, he obeys, he gets rewarded.
So what of a child? First of all, the same applies. I'm not a parent myself, but as a former child, I can attest to the fact that reason does not necessarily precede conditioning potential. I didn't always understand why I was being punished, but I knew full well how to avoid that punishment.
And that really is the problem. Especially for me as a naughty child, I couldn't always be reasoned with. When mum tried to reason with me, I'd try to "reason" back. And my reasoning, as I now understand as an adult, was stupid. Very very stupid. Discipline was the only thing I would respond to. I needed discipline, and I got discipline. And as an adult, I am now very grateful for it.
Why would I be grateful, you ask? Simple: A good parent knows how to adequately discipline their child, but real life shows no such restraint. Who would you prefer to learn about road safety from; a cane, or a car? Who would you rather teach your child about theft; your right hand, or the police? Should a violent child be allowed to enter adulthood with his habits intact, or should violent tendencies be met with "violent" responses? And let's be honest here: It's not really that violent. Of course there's an issue when it actually is violent. Woe betide the abusive man who actually harms the child. But woe betide the man who fails to drive bad behaviour out of his children before the world does it for him. Discipline is not child abuse. Failure to discipline is.