I don't call a corrective cuff violence. As I said, what I'm talking about is not about hurting the child. We're not talking about flogging.
Of course there hasn't been a study showing that an occasional smack improved a child's behaviour. Such a study would be impossible to design.
The point is that occasional physical correction, such as the lion cuffs I mentioned earlier, don't do any harm, not that they do any good. In other words, the result is neutral. It's not bad, nor is it good. It's harmless but, on occasion, effective for the particular moment concerned.
And, once again, I'm not advocating it, just saying good grief, calm down, to those who are shrieking as if it was abuse.