Why does Stella Creasy respect these women's right to congregate separately from men, but also not respect women's right to congregate separately from men?
Because the first concerns freedom of association under Article 11/Schedule 16 (and is perhaps also covered by the religious exemptions that permit separate worship and male-only officiants).
Whilst the second concerns single-sex services under Schedule 3, WR1992 etc.
Also, how can the Equality Act protect the rights of women if it cannot clearly define sex?
I agree that it cannot, but Creasy is in the grip of a metaphysical belief about the meaning of sex which she thinks morally right to impose on the rest of us (it isn’t – see Article 9).
And finally, does she not realise that the EHRC interprets the law but does not make the law, and that if she wants the law changed she will need to put forward legislation?
Well maybe, or maybe she accepts FWS but thinks, like RMW, that transwomen should be a special exception (like small children, plumbers, cleaners, and emergency workers). I don't agree, but it's not totally incoherent either.
(There's a wider question of why TRAs don't lobby for a law change, resorting instead to stalling tactics, lawfare, creative reinterpretation of FWS, and rank insubordination. I asked a transwoman friend: it's because it would require them to debate and negotiate openly with people who disagree with them, and this would be like asking the Jews to negotiate with the Nazis. So, now you know.)
I don't think it's fair to characterise Creasy as stupid or evil. She's dealing gracefully with the torrent of shit being directed at her on X. And it's her job to engage with Muslim constituents, amongst others. To those sneering at the 'future engineers' comment, what are they doing to mitigate the harms to adherents of minority religions? The only way is through education, rigorous application of the law, setting a good example, and saying what we want to see. Encouraging a handful of Muslim women to see themselves as future engineers might be a drop in the bucket, but it's not nothing.