Gender identity refers to our sense of who we are and how we see and describe ourselves. For some, this can cause distress when sex doesn’t match up. and that’s gender dysphoria. No one should be told they have to be a certain way or look a certain way. But if they want to, then that’s down to them and being on something that stops that distress I’m all for.
Well, sure, but the issue isn't so much in people feeling/dressing/looking a certain way. It's in those people demanding everyone else act as though they also view them that way, whether they do or not.
If I decide that I feel 20 years younger than I am, that's one thing. I can dress in whatever the cool kids wear these days, give up my bad 90s pop for the latest big thing on Apple Music, and act as though my prefrontal cortex isn't quite there yet, and as long as I'm not harming anyone else I should be left alone to be my bad self. But regardless of all that, I would have absolutely no right to insist that other people see me as anything but a middle-aged woman playing dress-up.
An external identity is not something that is stipulated by the individual and imposed upon the collective consciousness of the world. Your external identity is largely out of your control and will be different things to different people. Some people will think "Oh wow. look at that middle-aged woman being exactly who she wants to be - good for her!" and others will think "look at that idiot trying to pretend she's still young, what a tool!" - and regardless, none of them will actually believe that I am a "real" young person. Any attempt on my part to make them believe that would be narcissistic in the extreme. And any attempt on my part to try and make them say it even though they don't believe it - to speak lies to placate me - would be narcissistic and sociopathic.