So, thank you for highlighting a great demonstration of the difference between sexuality and gender identity. Sexuality comes from your own knowledge of yourself. Gender identity requires you to assume something about other people.
Note that you could fuck up sexuality in the same way by using the same identity model, rather than having the concept of "homosexuality".
You could say that a man who fancies men is actually a woman, because what makes you a woman is fancying men.
But then you'd end up in the same sort of bizarro paradox circular world.
Because if two men fancied each other, then they'd both be women. But then they'd both be women fancying women, which would make them both men again. Their identities would oscillate continuously. I haven't computed the oscillation frequency.
The concepts of "men who fancy men" and "men who say they feel like women"* make sense. Having distinct words for those concepts make sense.
But the statements "people who fancy men are women" and "people who say they feel like woman are women" fail because they accept words as an input, and then change those same words, in a feedback loop.
You've held the microphone up to the speaker and either got a dreadful squeal of oscillation or a totally floating signal.
- Pedantic footnote: "men who say they fancy men" also makes sense as a category - but it's less useful than "men who fancy men". And that latter group definitely exists because it's very clear from behaviour whether men do or not - we don't have to always rely on self-report - and this is the sort of thing sexologists keep an eye on. (I recall one talking the other day about research into how many 'bisexual' men were actually bisexual - you can research that). Whereas there's no coherent definition of what a "man who feels like a woman" is - it's something internal to a man that's not testable, and probably not the same feeling in many cases. The "beetle in a box" concept...
Also "person who fancies men" is also a meaningful concept, but again, less useful than "woman who fancies men" and "man who fancies men" as distinct categories.
All these categories make sense, with no circularity, they're just of varying utility.