Friend shocks me by suddenly saying he's female. How to handle this?

Obviously not true (hence why they're your ex, I assume). But irrelevant in the public sphere. The chromosomes of the people we interact with in public or at work aren't anything to do with us.

It's more analogous to covering my shoulders in church even though I'm not Catholic. It's just being respectful.

That's a choice you make when entering a Catholic church. It's more analogous to a Muslim co-worker insisting you cover your hair at work where you have no choice.

I think if you are willing to call a man she it is an all or nothing thing. You can’t pick and chose. You can’t complain when a male rapist is called she or criticise when someone says ‘her penis’. It is not any women’s fault that the worst men have been calling themselves women, but as they are allowed to it’s a problem which affects everyone.

No, there hasn’t been a “referendum”. There has been polling and consistently the message is the same and the trend for supporting these men in women’s spaces is a downward one. The first poll was 2018 and there have been regular polls ever since. Is that good enough, or is the fact that many women don’t consent felt to be enough here?

Again, why were stonewall and all the trans charities and allies not sorting this? That should have been their goal from the start. Transpeople need to take it up with them. It’s not women’s fault that trans people were let down by their allies.

Access to those spaces at all? For example, if a trans woman can't use the woman's toilet or the man's, what are they supposed to do? Therefore, they don't have equality, practically or legally. A solution would be to have gender-neutral spaces, imo would be fine but unfortunately the infrastructure isn't there yet.

You seem to be starting from the premise that there is symmetry. Transwomen in women's spaces is very different from transmen in men's spaces, as evidenced recently by the awful case of the transman being put on a male psychiatric ward and raped within an hour of her arrival. However, men and women may both want and need their own single-sex spaces.

The For Women Scotland Supreme Court case started with the Scottish government moving to address the underrepresentation of women on public boards - you yourself mention women in careers/leadership roles - but then saying that any man who said he was a woman could take one of those "women's" places.

I don't see how your feminism can include men taking rights and places away from women.

But women are the oppressed group within patriarchy. We don’t have equality, let alone equity (which is actually what is needed), so giving away the small gains towards equity that women have made to a subset of men (many of whom don’t need than and are happy to benefit from patriarchy when it suits them- look at Phillip Bunce and Eddie Izzard for just two examples) just sets us all back.

Would you use similar arguments to say that white people should be allowed to access spaces and programmes that have been created for people of colour? If not, why not?

Well, as his been explained many times, there are categories of women who need single sex spaces to fully participate in daily life. Why does the desire of a man to access female spaces trump their right to a single sex space?

But isn’t fighting for trans peoples accommodations what Stonewall et al should have been doing all along? Rather than bullying women into giving up their rights, wants and needs? If “rights aren’t pie” then why does giving trans people the right to access spaces designated for the other sex remove the other seeds rights to a single sex space? Why should the desire of a TIF to access mens spaces trump the right of men to have a single sex space ? Would you be in favour of TIF being sent to male prisons, psych wards and changing rooms? Do you think they would be safe?

Potentially, yes, I agree with you. That would depend on whether a, mine is actually the minority view. afaik there's been no referendum on this. And b, whether trans people have accommodation to make sure they have equal access to everything they need as well.

Yes. Feminism is about equality, ie how women used to not be allowed to have bank accounts, or how sadly we are still not seen as equipped for careers or leadership. If trans men can use "men's spaces" then there is no inequality. The question then becomes if a single-sex space is an accommodation towards equality, like a ramp for wheelchair users. What, then, is the accommodation that women don't have without it?

Thing is, if you don't cover your shoulders that doesn't potentially lead to a situation where you get screamed at/receive death and rape threats/are physically attacked/lose your job.

Also, the argument that there are very few trans people isn't convincing. You only need one, in any situation, to change everything. One trans-identifying male in a female sports competition takes the prize from every other woman and girl, and tells all other women and girls coming up through the ranks that organising their life around this effort might not be worth it because years of striving will go to waste if one man decides he wants their prize. And if you don't personally care about sport, and can't understand why it's important for other people, one male in a women's prison impacts every single, most-vulnerable, woman there.

As you say that you understand how other women feel about men in their spaces, and it “doesn’t bother you”, then as yours is the minority view, women’s spaces should be single sex, shouldn’t they?

Im doubting that coming out as trans changes who you are.

This friend said they would like people to use she/her pronouns. They may still have the same interests and hobbies, values and morals.

They arent in my mind any more "someone completely different" than if a previously heterosexual friend said i actually want people to know Im in a same sex relationship now. Being trans is part of this person's identity it doesnt make them a different person.

And even if elements of them change, elements of people constantly evolve age, beliefs, circumstances influence your beliefs, interests and priorities and can change them. So small changes happen all the time

That’s exactly what I was going to suggest. I think he’ll try and debate and persuade with his newly found zeal, and you just say you’re not interested in discussion, those are your legally held beliefs. That way you’re putting the onus on him to decide whether to end or continue. If you continue, you’ve made your stance clear, so hopefully less awkwardness. If he terminates then it’s his choice to be non inclusive of those with GC beliefs.

About your project, your colleague is highly likely to 'move on' from his traditional field of expertise and be concentrating fully on his new trans life.
He might volunteer this or you could nudge and use the 'bekind ' approach, in a let him have the space to explore his new attitude to life without being dragged back to the old hobby.
Frame it as Hairy Dave's decision when you look for a new collaborator.
But keep notes about conversations because when the ne' becoming a woman' project doesn't unlock all hopes and dreams and riches, he might turn back bitterly.

As a feminist it doesn't bother you that men are in womens single sex spaces as long as those men say they are women?

The gender critical position is worth of respect in a democratic society. Tell him you are gender critical and that while you will do your best to accommodate his preferences out of professional respect, human beings can't change sex. Then let him decide whether he wants to remain working on the project under those conditions.

Honesty is always the best policy.

So what human rights would transpeople lose?

That’s what I thought with my ex. Nope. Total capitulation, including stating I now believed he was fully female and I was now a lesbian….

I guess from my perspective, I don't understand that. It wouldn't bother me at all if a trans woman were part of any of those scenarios, especially considering how small a demographic it is (although I do understand why you might feel differently). My view is that women's rights should be elevated to reach human rights (freedom from discrimination, from violence, etc.), not human rights brought down to meet women's rights. I fully get why this is emotive for a lot of people, because women deal with so much injustice and pain. But to me it seems like a strangely niche side quest from the most severe ways we continue to fail women as a society, ie the reasons we need single sex spaces to begin with, that single sex spaces have not fixed.

Considering the person has gone public with a statement that they are now someone completely different, it's hardly an unreasonable stance!

Or are you doubting their authenticity??

The right to convene in women only groups without male presence
The right for single sex female only changing rooms without male presence
The right for single sex female only prisons separate to male inmates
The right for male crimes not to be recorded as female crimes.
The right for single sex female only refuge centres separate to males
The right for single sex female only hospital wards
The right for single sex female only sport
The right for single sex female only categories in awards and sponsorship

Literally anything that is labelled for women only, we have the right for it to be for women only, not also open to men who self identify as female.

Couldn't agree more.

The desire to totally control the narrative and to be abuse when trying to do.

I also think the issue just isn't that deep (not the whole trans / GC argument, I get that THAT is deep).

The crux of the matter is that the friend has expressed a viewpoint the OP hugely opposes and that it means they can no longer work together.

So don't work with them. It'd be a bigger issue if they were employees of a company and were forced to coexist. But they're not. Walk away.