@HairdryerMary “Why wouldn't they completely lose track of reality and become Japanese or Guyanese or Senegalese?”
Well, at least men can be Japanese or Guyanese, or Senegalese. The complete loss of reality is to claim that a man can become a woman. And, vice versa. You can change your nationality, and add nationalities, but you cannot ever change your biological sex.
If someone said to me they were the other sex, it would be on a par to them presenting their toothbrush and saying “That’s my dog. Please pet my dog, and give her chinny scratches”. I’d have to suspend any notion of thinking such a person was honest, rational or trustworthy in any shape or form. That’d just be my honest thoughts on someone making such a preposterous claim.