Unless the human body has changed sigificantly since I took Biology in the 9th grade, the males of the species don't have uteri, cervix, ovaries, or fallopian tubes. So how can it possibly be "medically necessary" to remove something that the patient doesn't have?
That's because you're getting the language mixed up. A "transgender man" is a female who ID's as male.
So said patient has a uterus. At least until it was removed.
I'm going to say that my feelings on this are "muddled". If, as mtnbkr mentioned, it wasn't removed in the original transition, but a medical condition popped up requiring it's removal later, I'm not sure I'd want a doctor who's refusing to perform a
medically necessary procedure that they'd presumably do if the patient ID'd herself as female.
This isn't helping somebody transition. Which makes the question of 'against their medical judgement' rather strange given that example - if the doctor truly thinks it's not medically necessary, of course they should have the option of refusing.