I'm about 40. I was spanked - rarely, and with I'm pretty sure reasonable cause. I don't recall being spanked after 9ish or so, I think. I fail to see how it brought harm, and would guess that my present self-discipline is an interiorization of the discipline I received as a child.
The article gives no source for the 80-90% number (although I found that 90% have reported being spanked) - and indeed, others readily available indications suggest those who have children age 2-12 now and used corporal punishment of any kind is presently far less than that, in the 60%s.
The original article reference Sweden, saying that it was already considered 'passe' by the time it was outlawed in 1979. As a sociological note, crimes per capita has increased steadily since 1960 http://en.wikipedia.org/wiki/File:Anm%C3%A4lda_brott_1950-2005.svg
, specifically tripling in that time. Correlation is not causation, I'd admit, but neither is it necessarily unrelated.
I fail to see the moral equivalence you draw between the disciplining of children by an, at least, well-intentioned, rational and loving parent (ignoring those who go far beyond discipline into abuse, because of whatever psychological damage they have), and the execution of them by uncaring, murderously self-indulgent mothers and the medical industry who enable the unjust killing of the innocent in vast numbers (1.28 million abortions, disproportionately black, for 4.25 million live births from 2006 US Census, more recent numbers haven't been permitted to be published).
What I do see as equivalent is the selfishness of the above, and the selfishness of those who would not discipline their children because they refuse to be seen - by their children or by themselves - as "the meany", when, indeed, perhaps that's exactly what the child needs for their proper development, instead preferring to hold some notion that makes them nicer than others. Obviously, circumstances are different in different children, and boys and girls themselves are different and require different forms of discipline - as well as role models of both genders - to thrive.
I'm put in mind of the more recent studies (since the 90s) showing that, not just in relation to girls (which could be attributed to girls doing better) but as an absolute, boys are 'falling behind' in many measurable areas. Many see this sort of discipline question as a particular correlant as to why they might be.
I would suggest, since the 70s, the gender deconstructionists of the power-dialectical wing of the post-modernist movement have done a pretty significant job at attempting to instill a revulsion of the masculine virtues in the modern mind - including discipline, offering instead indulgence as the rule and discipline as the atavism - preferring to hold up as models the waxed metrosexual or the limp-wristed "sensitive new age guy" - particularly womanly examples of men, it seems to me.