The definition of a true statement is that the words used match the observed physical reality.
The same would apply to feelings & identities. They can be deemed valid or invalid by cross examining the observed reality.
Recently, someone explained that gender reassignment was permissible since it's a cure to gender dysphoria, which they defined as: "A condition in which their assigned sex at birth does not match their experienced gender identity." Note that the above definition requires the physical to align with the identity. It renders identity as an objective and fixed reality, whereas the observable body as secondary and malleable. All of this is a judgement call on the nature of reality. It's a conclusion we do not accept. In our definition of reality, we look at which came first? The body or the feelings about the body? We ask which can be proven and which can't? The body is the root. The feelings about it branch out from that. Branches follow roots. Roots don't follow branches. The subjective is subordinate to the objective. The correct phrasing of the problem would be: "My feelings (which are subjective & malleable) are not aligned to my body (which is objective & fixed). What's the cause of this dissonance, and how can I ultimately align my feelings with my biological gender?" As you can see, before this is ever a legal discussion of Sharia, it's first an ontological discussion about what's more real than what. What is objective and what is subjective. If discussing this with an atheist, all we can say is that that we differ on ontology, on what's more real than what. But more than that, the secular justice movement is swindling the Muslims by selling beyond the close. And many of us fall for it. Namely, they ask us, "Shouldn't you be inclusive of transgender Muslims?" By discussing inclusion, we've already moved past the real question: is the concept even legitimate? (Trump did this when he said "Mexico will pay for the wall!" People angrily objected, "How will you make them pay??" Subconsciously they've already moved past the legitimacy of the wall.) But if talking to Muslims, we can easily say that the Quran renders the body as an objective part of our reality, drawing on verses about our creation as biological males and females. If you claim gender identity as a priority over biology, bring us a proof from the Book. Forget it being a priority, I challenge them to just find me a single reference to gender identity as it is used today from the classical sources. There is none.