Essentially he's making the same blindingly obvious point that emerges from this excellent 5-year-old article I've linked to many times (as have others). It's quite long but from about halfway Meghan Murphy reports on the travails of the Deptford Project after Goldsmiths students got involved. https://www.feministcurrent.com/2018/03/23/leftist-women-uk-refuse-accept-labours-attempts-silence-critiques-gender-identity/
But during a discussion with Goldsmiths students about a community housing project, things blew up. Mcdonagh was verbally attacked by students after rejecting the new language being imposed on her community, called a “white cis woman,” then a “bitch and a “cunt.” A young male student tagged her in a post online arguing that the Women’s March should not allow women to focus on “the vagina” as it was “transphobic.” When Mcdonagh asked how he was defining “woman,” the man responded, “Anyone who says they are.”
This is when, she says, it all fell into place. “That’s what ‘self-identify’ means: anyone can say they are anyone… So, rich, privileged people can claim to be marginalized.” Beyond that, she asks, “How can we keep working class women safe if anyone can be a women legally?”