Despite all the commentary to the contrary, there is actually no hard evidence that the western world really changed its views on racism and eugenics after the revelations of Auschwitz.
It just could be that the people who had always opposed it got much more vocal and those who had always espoused it learned to curb their tongues ----- at least in public and in public opinion surveys.
(But do let me know when you have developed time travel and God-like powers to see into the darkest truest corners of humanity's soul, and can better firm up all this windy commentary.)
Until then, the view I espouse is that late 1950s and early 1960s civil right protests were as successful as they were, when earlier (bigger) efforts had mostly failed, was because the chief scientific opponent of universally shared human rights (Modernity) was itself fading fast.
I argue one had to come of age as a young adult before WWI's modernity-driven disasters to remain a fully Modernity believer ---- that places the cutoff birthdate date for such fervent believers around 1895.
So the last people in this age group were all out of the work force by 1965.
Yes, they could still be politicians, preachers, authors, control great wealth, but they didn't command army divisions or run police forces, run government civil services, be editors of big newspapers.
And the most truly fervent (oldest) believers in reductionism, racism, eugenics, what have you - the teenagers of the Victorian era - were all in nursing homes or had simply stopped breathing, by 1965.
None of this would have really mattered if 1965 Modernity's young new Initiates, born during the war years and now about twenty to twenty five, had panned out as they were expected to in 1940 .
That was the time of the first Futurama, which set about to predict and then bring about the kind of world it wanted its grandchildren to enjoy in 1965.
But the grandkids weren't buying Modernity's new game plan - as best presented in the 1964-1965 New York World's Fair and its Futurama II exhibit.
I mean some were (insert a big shout out here to Dick Cheney) - but decidedly sotto voce - while a larger number opposed its visions, some quite vocally.
The vast mushy middle of this youthful vanguard went along - as always - in the direction of the biggest noise.
Now as to why so many of the young Initiates stopped believing , I think one possible answer is that while Modernity actually delivered on most of its promises, a majority of the new young buyers (along with a lot of the oldsters) didn't actually like what was on offer.
I say this as a student of political science, where it will never do to simply imagine that all governments that lose elections, do so because they failed to deliver on their promises.
Many,many times they do deliver ('we will cut government services to lower taxes') and the voters then don't like the results....