There is a link, a strong link, between the post-1965 demonization of IQ research and the sexual revolution - and therefore with traditionalist Christianity (that is, Christianity which sees itself in continuity with the Christianity of the past 2000 years).
First there is timing - intelligence research, and specifically the ideas of group differences in intelligence and hereditary intelligence, is merely a quantification of universal common sense among humans.
Yet this universal common sense was denied and then inverted from the mid-sixties, exactly in parallel with the sexual revolution.
Everybody had always known that - for example - men and women have significantly different abilities and natures, and that these differences are intrinsic (inborn).
Everybody had always known that children - on the whole, on average - resemble-their parents in terms of abilities and personality - as well as appearance.
Research into intelligence and personality differences simply tries to put numbers to this stuff which everybody already knows and always has known
- yet in putting numbers to it, and making this knowledge thereby suitable for public discourse - there is inevitably a selectivity and distortion, as there is with all science.
There is a trade off, always, to getting greater precision - it comes at a cost.
The cost can be and should be discussed - the distortions and incompleteness need to be kept in awareness.
But the underlying reality remains.
What about the sexual revolution?
Well, just at the time when IQ research was being demonized, punished, vilified - so was traditional sexual morality.
This, again, was a matter of taking what everybody had always known and problematizing it.
In the first place,traditional sexual wisdom was not 100 percent correct - this was taken to mean that it was complete nonsense.
Secondly, it could be shown (sometimes honestly, often dishonestly) that different sexual traditions existed in different times and places.
But, instead of looking of common underlying features behind superficial differences, difference was instead taken to mean that sexual morality was purely arbitrary, and could be reinvented at will.
A whole style of evaluation thus developed - which now rules the public domain.
This involves pseudo-scientific micro-methodological critique of whatever disagrees with the prevailing anti-traditionalist, New Left, politically correct consensus.
100 percent perfection or outright rejection is the evaluation rule for opposed ideologies - meanwhile the prevailing ideology is judged by its expressed aspirations and intentions, and gross incoherence thereby excused.
Since the mid-60s discourse on sexual morality involves highlighting the individual exceptions, creating thought experiments which showed that abandoning traditional ideas/ knowledge would not necessarily lead to disaster, at least not to instant disaster - it was possible to imagine, at any rate, situations in which a complete sexual free-for-all and abolition of all previous distinctions was a part of a kind of euphoric bliss...
That was what much of late 60s popular culture was about - imagining this state of sexually free bliss; and thereby rejecting all of human history, knowledge, wisdom up to that point.
And the evaluation style which made this possible is precisely the evaluation style which made possible the suppression/ rejection of all traditional human knowledge relating to ability (IQ) and human nature (personality) - to the point of denying that there was any such knowledge at all, and that the whole domain of hereditary differences was one created and sustained wholly by evil motivations (thus providing yet another reason for rejecting traditional wisdom - closing the loop, sealing the fly bottle).
This is why an acknowledgement of hereditary differences in abilities and personality has become a litmus test not just of political seriousness and honesty, but a litmus test of traditional religion.
What I mean is that traditional Christian denominations and there adherents will, sooner or later, be confronted with decisions which either affirm the reality of traditional knowledge concerning hereditary human differences - or else, in rejecting this traditional knowledge, they will find that they have also rejected the evaluation mechanisms which enable them to reject the sexual revolution - at which point they will inexorably move towards 'liberalism'/ secularization.
Alternatively, if traditional denominations adhere to the evaluation methods by which the sexual revolution may be rejected, they will sooner or later find that these same evaluations will lead them to accept the reality of significant hereditary differences in ability and character (including between sexes and any relatively genetically separated human groups) - and this will bring them into head-on conflict with prevailing public morality.
This ought not to be a surprise nor a challenge for Christians who see themselves as adherents of traditional standards; but in fact it often is a very big challenge - since this aspect of dishonest New Leftism has seeped almost everywhere and assumed the appearance of scientific skepticism and informed common sense.
But that is precisely why it is a litmus test - sooner or later traditional Christians will have to choose between the traditional understanding of human differences which also enables and underpins traditional sexual morality; and the New Left relativism and cultural constructivism about personality and intelligence which will swiftly lead to embrace of the sexual revolution.