The only merit that I can see is that some people feel that gender should be nothing more than a description of biological or, at least, physiological sex.
It confuses me to no end that my very girly oldest child identifies male, especially since hearing them talk about it, it seems more a rejection of being seen as a sexual object than any desire to be a man.
If my kid wants to identify male while being born a girl and being super into makeup, dresses, and sparkle, and that helps them deal with their sexual abuse, more power to them. Even if it breaks my old person brain a little.
Nothing excuses hating someone or being angry because they disagree with you about the definition of gender. I mean, if a woman assaults another female person, the punishment should be the same, right? It's not like men can't go into women's bathrooms anyways if their mind is set on it.