The thing is, it's supposed to be virtuous to deny the evidence in front of you, look right at it and say what you are supposed to, which some would term as compulsion to lie.
Virtuous is exactly the right word. For most it's not done out of malice but out of a misconcetion that it's a good thing.
The framing is something like this:
"The sex differences we think we see are just something our culture has taught us to see. If we hadn't been corrupted by our culture we'd not see them at all, we'd see the "real" truth.
Those who are corrupted by culture (ie all of us) cannot help but "see" but we should ignore/deny that knowledge and act as if we do perceive this "truth", because then we are closer to what is really true and not perpetuating the cultural corruption.
Anyone who refuses to ignore the knowledge is choosing to remain corrupt and is irredeemable. The ones who not only continue to see but actively try to draw attention to it are the worst of all, they are trying to drag us all back into the corruption with them."
The worst of it is, some of it is right. The social constructions attached to sex (what GC people mean by gender) ARE exactly that...a cultural lens we need to learn to recognise and ignore. (Acknowledging that while the end goal is no differences between men and women except where directly required by our physical differences, within a society trying to become gender-free but constructed from sexist foundations, sex-specific social structures to counter that will be needed for as long as the underlying inequality is present).
The genderist misconception/slight of hand has been to frame all consideration of different needs or capabilities due to sex / sexism as invalid cultural baggage and then twist the path to acceptance and self-expression from "acknowledge and support immutable sex differences, fight and remove sexism and gender construction" to "deny immutable sex differences, celebrate gender construction"