Absolutely true. The fact of the matter is every kid is different and this is even more evident as we find out just how big of a role genetics play on our personalities. While it's normal for young children to be stubborn and defiant, some are far more defiant than others. You may be able to get away with not spanking some kids if they have the right temperament and respond well to other forms of discipline, but those are probably rare cases. Not to get too specific, but I see it even with my own kids. My oldest has always been pretty compliant and rarely required spanking. My youngest is practically the opposite, so he gets spanked more. You can't reason with a 2 year old who thinks it's funny when you yell at him for running toward the street. That's a life and death situation that needs a harsh response to cement the lesson into the child's mind. And it works.
Anyway, apparently he got this from a few studies done a while back that allegedly showed spanking reduces frontal lobe development. Of course, these studies came from anti-spanking libs/Jews in academia and are easily deboonked. One of them correlated low IQ in third world countries to spanking/abuse. I don't think I need to elaborate on why that's wrong here. The others simply didn't take into account the more probable explanation that the lower IQ kids were spanked more often because of their slower development, not that the spanking literally caused their brains to shrink. It's laughable.