Sure--maybe I'm not, and maybe I don't even disagree with you on the topic of trans identity. I do, since we're on this topic, think that there is a pretty good case to be made that people who know less can nonetheless have key insights or key arguments that ought to be sufficient to change the mind of someone who knows more. But you are of course free to filter your attention however you wish, and "at least be at my level before we start" is a reasonable way to increase the chance that the discussion will be productive.
I do sometimes do this myself. I try not to very often, because I think that one of the ways that people can contribute to society is to share their knowledge with people who haven't yet had the opportunity to gain that knowledge, and that part of the societal balance of different interests is that people should express their concerns from whichever place they happen to be and have that they are concerned taken seriously, even if the content of the concern ("there's a microchip in my vaccine") is not worth taking seriously. However, that's a personal choice; you can make a different one.
Anyway, that's all an aside. Thank you for the long response! There is a good deal to think about!
Regarding Truth, you say, "I specifically used a capital letter on Truth to signify a philosophical concept. You're using "truth" as a synonym for "accurate". I'm not." Okay, but you didn't say so originally. How was I supposed to determine what you meant with high reliability? (I'm still honestly not quite sure what you mean by it, but my original set of possibilities seem to probably not have included what you mean.) You could also have capitalized it to meant that it was deeply felt (this is more consistent with how you use it), or that you were using it in a formalized logical sense (i.e. logically True and False).
I'm not sure the distinction that you're drawing between true and True is well-illustrated by the $1.99 grocery store example. True, correct, and accurate are all partial synonyms whose meaning differs mostly in implication. But if you want the philosophical concept, the concept itself is far from settled anyway, so it's good to specify more precisely what it is that you're talking about. Is it an ordinary correspondence theory of truth, as part of an epistemology where knowledge is justified true belief? Probably not, or your statement would scarcely make sense. Is it a coherence theory of truth? That fits with your meaning, but if it's not a very carefully constructed coherence--certainly not the full-throated social construction of truth a la postmodernists--then all my criticisms apply in full. Do you mean that everyone gets to choose their own epistemology and we can't complain? But that too destroys in theory (if not practice, because people's revealed preference is rarely for the epistemology they state that they have, even assuming they know enough philosophy to state anything) the ability to have a common objective reality. So the window for a meaning of capital-T Truth that doesn't either render your statement patently absurd, or render my criticisms critically important, is pretty narrow: objectivity threatens from one side, while nihilism is a yawning chasm on the other.
But apparently what actually happened is that despite making a completely general statement, you seem to have meant for the context to imply that you don't mean this as a general rule for everything (despite phrasing it as such) because "you're arguing about things that don't fit the category I'm discussing". Well, no, quite right, I'm not! Because "The main logic is that we do not have the right to decide for other people what Truth is." sure doesn't sound like a category-specific rule. If you wanted to make it category-specific, you could have used, say, "their identity" in for "Truth".
So, anyway, I accept your explanation that it's a category-specific claim, but I hope you can also accept mine that I couldn't tell at the time (and, honestly, I still can't tell how I was supposed to know).
Regarding the what-is-a-woman issue, I think we agree that a crisp propositional definition is completely out of contention, and that people who think it can be defined as such are just wrong. You give excellent examples in that regard. And we agree that we're not likely to get a definition that society agrees on, and we agree that there's no underlying regularity that is so crisp that any other demarcation would be foolish (it can be the case that society insists on being foolish, but those committed to non-foolishness can get past that...but it isn't the case here).
However, where I think we might differ is what to do once this realization is made. The first step is to just embrace the realization. Sex is complicated, and it's not just two categories. Sometimes you can rescue the duality of things by specifying some property: P has a female bone structure, Q has male gonads. Sometimes you can't, or we don't know enough to even know whether there is a separation.
But you seem to end up denying that complexity and handing control back over to the person.
Huh?
If I have divided the world into circles and triangles--and most things are actually circles and triangles, if I come across an octagon, am I supposed to believe that the octagon is a circle? Or a triangle? No, it's an octagon! We just spent all this effort acknowledging that yes, there are octagons. We don't ask the octagon, "Hey, are you a circle or a triangle?". It's an octagon. We might ask it, "Hey, do you want to herd with the circles or with the triangles--we only have two herds." We might say, "Hey, for convenience, we really only have two categories, and sorry for the two-alternative forced choice task here, but do you want the triangle label or the circle label?" But that doesn't make the octagon anything other than an octagon. It is what it is, and that is not a triangle--though it is a polyhedron!--and not a circle--though the ratio of perimeter to area is pretty darn close. And if we then find a hexagon, it's not a circle, not a triangle, and not an octagon. This is why, for instance, we have names for most of the different unusual sex chromosome configurations: it's just different. In biology, pretty much nobody loses sleep over figuring out whether a mutant fly "is male" or "is female". You might have a "feminized male" or a "masculinized female" if you are experimenting with the sex determination pathway, but the question of "is a feminized male a male" doesn't even come up because it fundamentally isn't a sensible (or interesting) question. (Interesting questions involve things like "does dosage compensation still work properly" and "why doesn't gonad development work properly" and "what happens if we feminize only certain brain regions" and so on.)
So while I'm totally comfortable with resolving the "what is a woman" gender-identity issue in several different ways, I am not terribly comfortable resolving the "what is a female" sex-identity issue in any way that loses track of actually different states of biology unless we're all very very clear that "sex" is now, somewhat redundantly, yet another cultural construct and we need to use some different term ("biological sex" maybe?) to mean whatever-we-call-it-that-actually-corresponds-to-all-the-variability-out-there.
I completely agree with you here: "this is not the definition they are using when THEY look at people on the street and say, "That is a woman." [...] they're doing a quick calculation, adding up all the symbols, and punching out a result of "man" or "woman" or "I'm not sure.""
Yep. Absolutely.
But then you take a really odd turn, given all your criticisms of transphobes, because the logical extension of this sentiment is vehemently rejected by an awful lot of trans advocates. (Hard for me to tell what trans people themselves think overall (I know in a few specific cases, but that doesn't help), because advocates are loud: that's kind of the point.)
You say, "If they manage to do that all the time, so effortlessly, without problems... if they can accept that all these people are men or women, without knowing what their gametes are... they can do that without knowing what their genitals are."
Sure. But you've just enunciated logic that concludes that a trans woman who doesn't pass isn't a woman. Furthermore, you've just argued against having trans men in men's locker rooms in any case where the quick calculation might come out "nope, nope, definitely not 'man'". (Same for other permutations.)
There are a lot of "transphobes" who have that status because they maintain exactly this: you know a woman by looking, and you see, that's a woman. And you look at that trans person, and you know they are NOT a woman. And that's enough: they are not a woman.
So it's a pretty good argument, admittedly, but it's an argument that tends to be labeled transphobic.
Of course, the really virulent transphobes won't go for that. But the ones that post pictures making fun of the Wachowskis are totally down with that.
So I think you have an inconsistency somewhere.
You say you want people to get to determine their own identity, but you propose a what-you-see-is-what-you-are affirmation of identity, and you already argued (and I agree) that you really really can't see into someone's head to know what their own sense of identity is.
Now, maybe you're using this narrowly just to argue against transphobes who specifically want to know about genitals (or chromosomes??) and think they have an airtight definition for "who is a woman". Well, yes, it certainly shoots them down! But how do you avoid using the exact same argument on the statement "trans women are women"? The answer seems pretty clear: passing trans women are women, and non-passing trans women aren't. Or, if we admit that how we use words is a matter of convention (even if the reality described by them isn't), we can change the definition of "woman"...then...your argument isn't airtight any longer! All the transphobe has to do is make the additional declaration that they mean the surgically and hormonally unaltered (i.e. "natural") state. Fair's fair, right? If someone can argue to change "woman" to include trans women who don't pass the WYSIWYA test, why can't they change "woman" to mean natural unaltered WYSIWYA (which, they could argue, is what it always was historically anyway, because modern interventions weren't possible).
So I really don't think what you say you're arguing is consistent with the rest of what you appear to support. I think you actually need, logically, to come down very hard on the "mental" side of things as what matters. It fully supports your contention that you have to believe people about their identity (note--you're then committed to supporting Rachel Dolezal's transracialism; that's cool, right? Transableism too, yes?), and it coheres with a much larger fraction of the community that also is opposed to transphobes.
(Regarding "biology or the world" vs "biology and the world", I had interpreted "and" as constructing a larger set of evidence to pick from, because it didn't seem to make sense to require both things simultaneously. But anyway, if that is what you meant, you're quite right--my points were irrelevant. However, then a "yes" to your point three is a very weak statement--someone can reject anything that conflicts with their understanding of biology alone, and be totally fine. Also, paradoxically, they have to agree to accept someone's say-so when it clashes more with their existing understanding, but not necessarily when it does less. So I hope you can see how I ended up with the interpretation that I did.)
(Addendum: I agree with you about the futility of arguments where the structure isn't even logical. Quite right! But if you know in advance that truth-values are arbitrary, you don't even have to bother assessing whether the argument's structure is logical or not because it just doesn't ever matter. So you can skip all the wasted noise of talking about logic, too.)