Absolutely.
What is a legitimate interest? Why did this legitimate interest develop? Who is vulnerable in certain situations? And who is most in need of these services?
One that's recently come up on my radar is a males only group. They are a social group. One of the things they've done in recent years is focus on mens mental health and mens friendship. In a healthy way. It's about trying to encourage isolated men to find friends.
There are other groups available locally but this one is doing well precisely because it is 'blokey'. One of the blokes thinks it's a bit old fashioned and not inclusive.
I pointed out who it is inclusive of - recent divorcees, men who are single, men who just want to get away from the stresses of family, men who have certain health issues, men who have trouble with showing they aren't always masculine in the presence of women. He's fine - he doesn't have any of this shit going on. Introducing women to the pot would result in many of the others in the group self excluding. This doesn't mean they don't mix with women. I know them because of this group.
In our heads we've come to believe that inclusive just means protective characteristics. This simply isn't true. It's a much more complex thing.
It can be about identifying vulnerable people within a single characteristic and providing a support network around those particular weaknesses and issues.
These are important distinctions to be made.
In terms of social groups whether it is appropriate to exclude males from a female group. It would be more appropriate for them to have their own group to represent and deal with their unique issues separately without harming their own interests or the interests of women. That's the point.
If there's a women's only outdoor group and one of its stated aims to discuss the female body and the challenges this has doing outdoor adventures and how impacts like female strength, childcare, the menopause and female aging and health care as well as safety and two blokes with beards come up giggling and ask if they are welcome to join, I think we should be able to tell them to legitimately stop taking the piss and fuck off to the LGBTQ group who had their presentation half an hour earlier on the same day. (Real life situation) Instead we are supposed to sit politely and just suck it up and then end up self excluding because it's obvious no one has the backbone to say, this isn't appropriate for you and we serve a legitimate gap in outdoor activities that there is high demand for.