You don't have to say anything about his "gender identity" to enforce a professional dress code

In a sane world, this is true. But in woke Tranada (where men get to define what a woman is), this guy gets treated the same as a woman with naturally large breasts or a beast cancer survivor who wears a slightly padded bra.

Also, if you tell him mini skirts are against the dress code, he can just cry that mini skirts are the only things that cure his dysphoria and he'll literally kill himself if he can't wear them to work

But a large breasted woman wouldn't be allowed to have them sagging down to her hip bone with the nipples protruding through a shirt that's way too tight.

Also, we can accommodate people with physical differences that they can't help without extending those accommodations to the general public. For example, if a blind person needs their seeing eye dog at work, it doesn't give me the right to bring my pet to the office. If a disabled coworker needed and particular expensive desk chair, it doesn't mean the rest of us get an upgrade too. My coworker recently had a baby and was given a key to the lactation room and a break schedule, I'm not entitled to either of those accommodations, because I don't need them! Can I "identify as lactating" for the rest of my career and go nap in there?

If this dude can't behave professionally without killing himself, then he needs to be compassionately removed and sent to a psych hospital.