Dervel says 'And also the “lived experience” claim. It makes it damn difficult to make objective claims, when all someone has to do to rebut you is say “my lived subjective experience trumps anything you have to say”.'
I'd like to endorse this. I am not sure what the origins of this trend are but some part must have been played by post-modernists and deconstructionists, who have tried systematically to destabilize and delegitimize all sources of authority, so that ultimately all we are left with is either really complex "negotiations" (one of the decons' fav terms) between "loci of power" or someone's personal narrative, which can't be challenged because the narrator is the sole authority for it.
There is a parallel with "gender identity" here, though "GI Joe" or "GI Jane" is a real object, conjured into being by its owner. Gender has emerged as a kind of personalized Aristotelian essence—the "what-it-is-to-be-me", the τὸ τί ἦν ἐμοὶ εἶναι (the messentia?). Unlike subjective experiences, this is something objectively real; unlike a shared reality, this is something to which the owner alone has privileged access.
In short, they've come up with a metaphysical Catch-22. You can't see see this "feeling", or hear it, touch it, taste it, or smell it. There are no scientific instruments that can detect it (despite what some TWs claim there is no such thing as a "female brain" or a "female hypothalamus"). There is and can be no documentation of it, as a historical event can be documented. But it's nonetheless an unchallengeable guarantee of something absolutely real, they assert, and everybody else has to kowtow to the reality that the owner of the feeling is the sole authority for, who has then reified it, i.e. made into a thing. And made it into a Thing, too, given that everyone is talking about it.
This gives us the worst of relativism (there is no shared reality, so we can't disagree about it) coupled with the worst of naive realism (this is just something real, so we can't disagree about it), both in one ugly package. This might not matter if it concerned only a few academics nobody's ever heard of, but it doesn't.
Similarly, post-modernist thinkers attempt to construe every event in terms of power, with the only kind of power that is legitimate being an individual's power over his or her own life—which of course threatens to collapse into libertarianism.