You're using the word sex. There is a known, massively complex, relationship between sex and gender but it's not 1:1. For anyone. Or, if you think that's not true, then please describe to me how they're identical. In a group of men, in any place in the world, you'll find wildly varying accounts of what the male gender "is" all the way down to how their bodies should look.
And, gender aside, the most important thing to consider is the existence of intersex people, the diaspora of their bodies, and to consider how you think we should talk about them. Sex is, even outside gender, in fact not immutable. It's biology. These people are also historically denigrated.
Please imagine how ~150 years ago we collectively thought (and some people still think) that a person's race determined their intelligence. Historically "fundamental truths" usually end up with people being thought of as subhuman. The "fundamental truth" of sex, as it's presented by those who consider trans folks not people, is the same sort of truth. Biological sex is a spectrum, demonstrably. Gender is also demonstrably a spectrum. I don't care what people believe sex is or isn't. I care that we treat everyone, no matter how "weird" with respect.
And, gender aside, the most important thing to consider is the existence of intersex people, the diaspora of their bodies, and to consider how you think we should talk about them. Sex is, even outside gender, in fact not immutable. It's biology. These people are also historically denigrated.
Please imagine how ~150 years ago we collectively thought (and some people still think) that a person's race determined their intelligence. Historically "fundamental truths" usually end up with people being thought of as subhuman. The "fundamental truth" of sex, as it's presented by those who consider trans folks not people, is the same sort of truth. Biological sex is a spectrum, demonstrably. Gender is also demonstrably a spectrum. I don't care what people believe sex is or isn't. I care that we treat everyone, no matter how "weird" with respect.