There is nothing in your post that I have not already tried to convince the pro scp brigade in the last ten years. I have been unable to change anybody’s mind. They feel the benefit outweighs the negative consequences. You could compile a mountain of evidence of the negative effects of corporal punishment and they would still argue for its retention.
Why? Because contrary to what comes out of their mouth (or keyboard) they really don’t want to use another method because it involves actually finding out the reasons for the behavior and they just don’t have time or want to take the time. They talk a good game but all you have to do is eavesdrop outside a teacher’s lounge for a few minutes and you see how they really feel.