I don't believe people should need to cite 'safety' in order to justify single sex spaces.
I have an extreme example: I have (a long time ago) attended male-only sex on premises venues. I believe that the men who use this space don't want transmen in them, especially transmen who have not had any surgeries. Men are not afraid of transmen; it should be enough for us to say 'we just don't want them in that space'.
People need to justify sexist "single sex spaces" in the first place. YOU need to justify single sex spaces.
Now, you can certainly have your "private club", and everyone in the world is free to identify your "private club" as being full of shitty people that expect people to have surgeries to be accepted; that this is a fundamental shittiness, in fact.
There are ways and rules under which you can make such a private event. It does mean you are afraid of them afraid for some reason of having them in that space.
It is "sex based" discrimination.
And again, I'm going to iterate this yet again: you have no right to the knowledge of what is in someone else's pants unless they show or tell you themselves. I will acknowledge no claimed right to reveal that of anyone else either, short of their consent to do so.
I'm wondering if you maybe missed the fact that Metaphor is talking about a literal sex club. Like a place where gay men go and have sex with each other. Which seems like a perfectly reasonable venue to have a "penis required" clause.
Oh, yeah sure, if the offering is supposed to be "men with penises who like men with penises", that is a perfectly acceptable private club.
But those are hardly "public" events, either, usually.
That is literally in the bedroom. Granted most places I know wouldn't turn down a trans dude, and most groups, all but the most bigoted, old, moldy-dicked wart farms, have members who wouldn't say no to some horizontal action with a guy with a pussy.
Then, the last time I heard of a sex club running in my city, I had a friend who went and everyone there was just
sad, to the point where you could almost give them a pity fuck.
The cops raided it a few months later.
But the thread isn't about sex. The thread is about putting leather balls into nets or over fences, or whatever.
Genitals don't matter for that.
Neither do the interactions I have with the vast majority of everyone everywhere for any other purpose. I haven't had to know what was in someone's pants for any reason for years. I haven't cared. I haven't thought about it. I don't need to differentiate people on that basis with language. Most people seek to be differentiated for whatever social reason; they have people or ideas to emulate, and good on them for doing it. But I'm not going to assume what they "mean" by that, or "what that means" of them. They'll either show me, or they won't.
Personally, I think the meaning is just made up and the only people this confuses seems to be you lot. You haven't justified sex segregation except for the literal purposes of sexual preference in a sexual setting. Now do sports.
Because for sports, it's hormones. And only hormones, really: which ones you got, and for how long.