It seem obvious to me that there are people that can identify as something that they are not. — Harry Hindu
There is nothing new in that. Nero identified himself as the benevolent, loving emperor. Hitler identified himself as the savior of the Arian races. My neighbor identifies herself as the world's most beautiful woman. My mailman identifies himself as a caricaturist, I identify myself as a man with a very good sense of humor, you identify yourself as the master of Banno, and Banno identifies himself as a know-it-all.
Obviously in the above list the identities assumed to apply to the self are a far cry from reality.
It does not even need to be restricted to the human race to identify yourself as something you are not. For instance, my dog identifies himself as the lord of the manor, and my cat identifies herself as the person for whom the world has been created to be her playground.
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I believe that there are people who are truly repulsed by their own body, due to their sexual characteristics. This makes them reject their own sexual nature, and identify with its opposite, or with an alternative. This is not even arguable, there are tons of evidence to support this. This is akin to hetero men watching homosexual porn, or else truly gay men watching straight porn. It's a huge turn off -- and if your own body turns you off the same way and with the same intensity, what the heck are you supposed to do with it?
I believe also that there is not only strictly homosexual or else heterosexual attraction. There could be a mix of those affecting the same person. These are not changed over the course of life at any point, and one is stuck with this outlook practically from birth. This may be one reason to name sexuality non-binary.
And finally, those who are accommodated in questionnaires to name their "sex" with a choice of "male", "female", "other", "mix", "neither", "funny you should ask", "who wants to know", "I've hoped you could tell me", and "fuck off", are not the ones that decided to do this. It is done by the same philosophy of our leadership that bans hate speech, that encourages tolerance, that makes sure nobody has to die unnecessarily, and that people of any color, race, national origin or religion can fully participate in the social context of the countries in which the questionnaire is altered thus.