This "with us or against us" mentality is poisoning the Left.
Yes, it is purity spiralling in action.
I like this section from Jo Bartosch's latest work
4w.pub/the-fall-of-stonewall/
Whilst Stonewall have never pretended to promote a feminist analysis, until recently, the charity did not actively oppose the rights of women. Today, thanks to the inclusion of the ‘T’, Stonewall is campaigning against the Equality Act (2010), positioning themselves in opposition to feminist aims. With the meaningless strapline, "acceptance without exception" Stonewall has been very successful at positioning "trans inclusivity" as the liberal default for the bien passant. The result of this has seen Stonewall turn its attention to actively dismantling women’s rights in the UK; promoting the acceptance of men who identify as women in not only women’s single-sex hospital wards and prisons, but also women’s sports. Stonewall have even recently begun to lobby World Rugby to make the women’s game single gender rather than single sex; despite the fact that an independent report showed an increased risk of injury to women of 20-30 percent.
I think you would have to be quite selective in your definitions of 'harm to women and women's right' to not see those harms to women's rights that are being done in the name of being kind or having sensitive consideration of trans women because they are at the first instance dismissed as not women and therefore excluded from any woman centric idea or resource.
People who identify as transgender should definitely have their own set of rights and they should work to progress those and seek compromise where they conflict with others rights.