[...] Greer's belief that surgery can't 'turn a man into a woman' and the biological essentialism to which this commits her, is not just a hallmark of Second Wave feminism, but the very basis on which it sought to build a common movement. It's not some wacky metaphysical conceit she and many other feminists of her era happen to believe for no reason; it is, or historically was, invested with a tremendous amount of productive and positive meaning that made feminism possible as a project. Whatever criticisms of seventies feminism are warranted (I won't go through them because I don't have all day), it did achieve substantial progress for many women, partially enabled by this belief.
The burden of reproductive labour that has characterised women's oppression—sexual availability, pregnancy, birth, childrearing, housework, the constant threat of rape and assault—arises, on this account, directly from biological causes. It's not hard to see why the existence of trans people poses a challenge for Greer; if she accepts trans women as women, her account of the material basis for female solidarity—biological sex—is extinguished. Her rejection of the legitimacy of trans identities is therefore a sort of cipher for fears about the stability and cohesion of the 'women's movement' as a whole.
Of course Greer is seriously misguided with respect to her specifics. Biology means nothing in a vacuum; only the forces of culture and society intervening on biology can be said to produce any meaning at all, including oppression. 'Female bodies', which she defines as bodies capable of pregnancy and birth, only become the instrument by which women are subjugated when patriarchal social forces, the class interests of men, act to produce this state of affairs. This might seem an insignificant point, but it really is crucial. When Greer refers to women's biology, she is referring to a constructed set of meanings that are produced by oppressive social forces. By reifying these meanings, she implicitly accepts a model of women's bodies that is created by and serves the interests of patriarchy.
Similar oppressive forces shape the meaning of trans women's bodies, and produce trans misogyny. That's why it makes complete sense for non-trans, or cis, women to take trans women at their word regarding their identities: what we all have in common is that our lives are shaped by the operation of sexism. Cis women's occupation of an inferior spot within the gendered hierarchy is also the only thing that we all have in common. It's class all the way down.
When Greer says trans women aren't women, she is policing a line of demarcation she perceives as the enabling force of collective struggle. Unfortunately, what her words effect is an attack on nascent forms of solidarity she doesn't understand.
