Earlier quoted context omitted.
Affirmation-only in the form of behaving as if women and transwomen are indistinguishable is not always productive. For an example, if you write a feature telling people to watch and cheer on women speedrunners but you only include people who were successful male speedrunners before their transition you are not encouraging more women to join the hobby.
Obviously cis and trans women are not completely indistinguishable -- they have overlapping but distinct medical needs, for example. This is a strawman position. However, GCs tend to believe in an oppositionally sexist view of the world, where your assigned sex at birth puts you in one of two firm categories, and any sort of crossing over or breach between categories is impossible. That's how GCs construct their cate…
Sexism is “prejudice or discrimination based on a person's sex or gender. Sexism can affect anyone, but it primarily affects women and girls. It has been linked to stereotypes and gender roles, and may include the belief that one sex or gender is intrinsically superior to another”.
GCs reject sexism. Rejecting sexism doesn’t mean rejecting the reality of men and women being genetically distinct and having different body plans for the purposes of reproduction. Rejecting sexism doesn’t mean refusing to discriminate when discrimination is necessary for the socially just goal of sexual and gender equality.
Sex is recognised at birth, not assigned at birth - it’s determined at fertilisation: XX or XY.
Assuming you’re a transwoman. Your sex is male, and your gender is feminine. Women and transwomen substantially share a gender, given most women choose to be feminine and most transwomen feel compelled to present and be seen as feminine.
This is fine, every GC person I know accepts the right of individuals to choose their expressed gender and be free from unreasonable discrimination. What we don’t accept is the refusal to acknowledge that women also have a sex-based component of identity that transwomen don’t share.
I appreciate that this causes psychological stress to people with a dysphoria that is only calmed by affirmation of successfully changed sex - but - the physical reality of the situation can not be changed or rationally denied.