I think part of it is what happens when people take post modernism and the sociological turn in philosophy of science too seriously.
In one sense I can see why people end up in these extreme relativist positions about scientific knowledge. I used to joke with my students "Bacon said the possession of scientific knowledge could be used to gain political power, Foucault says that having political power gives you the power to decide what is allowed to count as scientific knowledge." And relativism and scientific constructionism are very plausible positions to adopt with regard to some of the softer ends of science - sociology itself, psychology, economics. Why is one generation's mental illness (hysteria as wandering wombs, homosexuality as mental illness) another generation's clear example of prejudice at work?
But, although there have been brave attempts to apply social constructivism to the hard sciences (physics, biology, even maths), they're never terribly convincing.
Major digression alert - failed attempt to do social constructivism on physics and maths. For example, Andrew Pickering made a brave, but ultimately failed (IMO) attempt to tell a social constructivist story about particle physics in Constructing Quarks. It didn't really work because in the end even though Gel Mann introduced quarks as a purely fictional device to systematize the data, and physicist joked about the "November Revolution" which makes it look like it was a political decision (the discovery of the J/Psi particle and that charmonium had an energy spectrum like that of an atomic nucleus, only a few orders of magnitude shifted up the energy spectrum), ultimately it was the physical world and experimental findings which carried weight. (And the rest of the book reads like a straightforward, old-fashioned non-sociological history of particle physics. Also I always found his claim that "this is the history of white men" a bit weird, given that a lot of his scientists were Chinese and Japanese, and he left out one of the greatest pieces of experimental particle physics, Madam Wu's discovery of the helicity of the neutrino). And even Pickering had to admit defeat when trying to do the same with Hamilton's quaternion theory (the forerunner of tensor analysis). There just turned out to be limits on the story you could tell within maths which seemed to do with maths itself rather than the belief sets and prejudices of mathematicians. At some level, the world just wouldn't play ball.
Then back to the point of this discussion...
And that's the case with genetics I think. Tell all the fairy stories you want about the supposed gender significance of intersex conditions, it won't impact for a moment on the fact that at the interface between genetics and evolutionary biology, a chromosomal set-up which deviates from the normal XX/XY binary, and which leaves the person with that chromosomal set-up infertile as a result, is not an exciting "third sex" but is, in evolutionary terms, a dead end, because the person with that condition cannot produce offspring.