What's always irked me most about the "mental health problem" diagnosis is the "so just snap out of this nonsense" attitude that typically goes with it. Even if it were a mental health condition, they don't typically go away after a quiet chat and some happy pills. Long term mental health conditions are managed rather than cured. So even if being transgender were a mental health problem, anyone with an even slightly open mind would have to acknowledge that perhaps the best treatment is to allow the individual to live in the gender role that makes them happy.

Of course we still get a mention in DSM-V, which is a book specifically about mental health disorders. However "Gender Identity Disorder" was replaced with "Gender Dysphoria." I would contend that it's the dysphoria that's the mental health issue, and that you can be dysphoric (deeply unhappy) about just about anything, including your job or your relationship. This can be a useful comeback when someone throws DSM-V at you.

A round of success for the LGBT+ community.

Done and done.