You seem to be under the impression that registered political parties are free to have any opinions under the sun. This is not America.
It is illegal to have a secular political party that discriminates on the basis of race or sex. As the BNP found out.
www.equallyours.org.uk/ehrc-legal-action-against-bnp/
Labour ran into this issue with anti Semitism. If the Greens lose any of these cases they have coming up then the EHRC may get involved. On that basis the Greens will be screwed. The issue is that a lot of the time Gender crits just say normal things like men are biologically stronger than women and fanatics take this as hate speech. When it isn't. They specifically are targeting one set of people with particular opinions, mostly women, after they win internal elections.
If Emma had said hurtful things about a particular person then you can get her on hate speech but if you make generalised statements based on science then it isn't. Being gender crit is fine and 100% part of British life and you can't pretend it isn't. It is illegal.
If you want to have an anti GC party you might be able to do that, but your best bet if you organise from the beginning around a protected characteristic like religion because gender ideology is not rational . Like the UK has various religious parties which seem to get away with a few things. Likewise you can advocate for removing religions from public life as long as you focus on all of them and not pick out one set of people. The Greens however are supposed to be organised around environment and social liberalism. This sexist perspective is an issue for them because the party is designed for open debate and discussion.
The Greens constitution actually bans a lot of the discrimination that Emma is suffering from. As always there is a conflict over rights here and it seems very likely the Greens are running towards a brick wall because they are unable to tolerate disagreements.
The Lib Dems recently had to rewrite their transphobia rules because they legally did not hold up. Testing this stuff in court is not going to go well for the Greens.