This is again the core of the question we keep coming back to and have never got a meaningful or satisfactory answer on.
This is not a trap, a setup for a gotcha, or any other form of dishonesty or subterfuge. It is an open, honest question I want an open, honest answer on.
Let's take the big 3 things that form the core of this discussion off the table for a moment. I'm not denying them or dismissing them and will revisit them, but I want to remove them from the discussion just for a moment for some context and points of view, fair?
So sports (i.e does Person X play in the mens or womens league), bathrooms, and pronouns just... put to the back burner for now.
I've asked this question multiple times. There is a person standing in front of me that traditionally has been identified as a biological male. This person informs me that they identify as a woman. For this concept to mean anything some concept of how I functionally treat, not just internally conceptualize but functionally treat, this person has to now change.
What changes? It's not a hard or unreasonable question. I know have to treat this person functionally different because I have been given this new, valid information about them.
So what do I do? What do I do, not think but do, differently? It's not important (at this point in the discussion) what this things is, but we have, have, have, have, have to agree that there is something there. We'll call this "Factor X." Factor X, whatever it is, is what differentiates a biological man who identifies as a man and a biological man who identifies as a woman. We can fight about what it is all day, but we can't fight that it has to exist.
I initially considered the person in front of me a man, they have informed me they identify as a woman, so "Factor X" changes. Okay. Let's roll with this.
We now have to accept Factor X as a valid difference between men and women. We have put a difference between the genders on the table and we cannot take it off. No amount of hemming and hawing or "it's not that simple" can make it so a valid difference is not transferable.
If I treat this person differently because they identify as a woman, I have to factor in that difference in how I treat men and women. Factor X is know a valid point of distinction and difference between men and women. You can't make that not true. If a biological man having that factor validates his identify as a woman, it is now an identifying characteristic of being woman.
The entire concept of transgenderism is trying to create inherent factors in the... sexual dimorphism of the human species that we only use in "identity" never in any other context.
Person A is a biological man. He identifies as a woman. This identity changes something. That thing is X, whatever it is. X is now a valid difference between men and women. A woman who doesn't have X is less of a woman. A man who does have X is now less of man.
If there is no "Factor X" this whole thing is the longest and most pointless thing since "is a hotdog a sandwich?" And honestly since if history holds true people are going to fight me on defining X in equal passion to arguing X simply has to exist, that's still the thing I'm leaning toward.
It's vitally important that a biological man who identifies as a woman and a biological man who identifies (or defaults) to identify as a man are treated differently, but it's also vitally important that we don't actually define what the a difference because then to not be thinking at random we'd have to treat men and women differently based on that same criteria and nobody wants that.
So a biological man and a biological woman I can't treat differently, but a biological man and a biological man who identifies as a woman I have to treat differently in some way that will literally never be defined even though that differences has to be exactly the same by definition.
This is not tenable. There cannot be no differences between the genders and sexes (that aren't already accepted as purely biological) but differences between the concept of gender and sex that don't use the same criteria.
And if I'm wrong about literally all of this we eventually do have to start defining these difference beyond "Whatever the transgender person says they are, we just have to believe them and can never question it, and every single case is its own case with no consistency or standards needed.
Okay so having said all that let's revisit the core practical applications of this; pronouns sports and bathrooms.
Pronouns. Fine after identifying as a woman I have to refer to this person using her/she pronouns. No problem if means that much to them I will certainly do so. I have some issues with how much of an "attack" misgendering is often presented as, but even with thinks I don't fully get I am not the kind of person to deliberately do things that other people find uncomfortable or insulting.
But... pronouns are weird. A lot of language doesn't even have them, don't have gendered versions of them, or implement them in radically different ways. So we have a civil rights issue that is language dependant? That's... weird.
Bathrooms. This person is now going to use the female bathroom instead of the male bathroom. Fine, I don't care in the slightest. But I don't care which bathroom anyone uses. The idea that feces and urine expression have to be segregated is stupid. A woman who identifies as a woman is as welcome in my bathroom as a woman who identifies as man. Just wash your hand and remember to courtesy flush if necessary.
But again under the framework of the transgender argument woman who identifies as a man going into the men's room and a woman who identifies as a woman going into the men's room have to treated differently, one has to be more welcomed then the other and... well I don't agree. So again I'm doing the right thing but not for the right reason.
Sports is the most complicated but oddly enough for me the answer is simple. Sports are entertainment. The answer is whatever people want to watch. If nobody wants to watch trans-athletes compete in certain leagues they simply won't watch, the leagues fold, and nobody wins in that scenario.