I am NOT a social scientist but I have this as an observation: The generation that produced the "Greatest Generation" had almost unanimously a "spare the rod and spoil the child" belief. If they produced the generation responsible for keeping the entire world free from Nazism and Facism then it stands to reason that an assumption can be made that spanking does NOT have the adverse effect that MOST everyone agrees with today.
Conversely the "Greatest Generation" (they mostly did SPARE THE ROD) is responsible for the 'flower child generation'. They planted the seed for the Dr. FeelGood, do your own thing, do gooders that followed Dr. Spock et al religiously producing what we see today as the PC world gone amouk.
Of course this is just this one man's opinion, I could be wrong!!
You are very right....like bullseye right.