@freemo Well I would argue that sex can be changed, depending on what we mean: at the moment, genotype can't be changed. But phenotype, what we actually see and what is actually there? That is fundamentally alterable without working at the genetic levels.
Because what is sex but a collection of different traits? Traits which, given the low sexual dimorphism of the species generally, can be altered surprisingly easily. We aren't gorillas. There the males and females are extremely different physically and behaviorally.
We're more like bonobos; if you didn't pay attention to the obvious physical difference you couldn't tell which is which.
@freemo For the liberal or even radical I'm talking about, to them gender is nothing more than societies gendered expectations of men and women, defined cisnormatively (simply treated as a brute fact by them). Will they defend the gender nonconforming cis man and cis woman? Of course. But they will treat the trans person as, at best, a victim of gendered expectations engaging in self-injury. At worst...well I need not spell that out.