They ought to quit looking so hard at the elements that go into raising up a functional, gracious, poised, talented, confident kid -- and look rather at what appears to work for each kid.
I am sure there are kids somewhere that require little or even no physical/corporal punishment in the mix -- but I have never met one.
I have, OTOH, met several kids I found to be obnoxious, out-of-control, who wre raised by parents who never ever ever spanked them.
Then there are the kids who got liberal doses of spanking and swatting and thumping, which might have been misapplied, since the kids were still obnoxious brats.
It's not like there's a secret, inflexible formula. What works in your household? What gets you the end result you want in your kids?