I do not trust these medical professionals. There are too many cases of kids who were guided into transition by them and came to regret it. As a recent example, there is a gender clinic in the UK (Tavistock) which is funded by the NHS, currently being sued for malpractice on this front, reportedly with thousands of clients involved.
As a medic myself, I don't trust these "medics" at these "hospitals" either. I consider most of them glorified butchers that will face justice once the political climate shifts - and it will, all is cyclical -we used to treat these cases psychiatrically not long ago and we isolated them, instead of affirming and normalizing.
However, I would advice not writing hate mail or phoning in just for slurs. These are ineffective, cheap moves, and gives them crybully ammo.
Be calm, dispassionate, cold even. Mention that gender is an inner feeling, while biology is scientific fact that can be detected across mammals, human cultures and history. Gender is modern dust in the fart-winds, only in the heads of catboys and "gender non conforming" populations, i.e. what we used to call deviant paraphiliacs just 30 years ago.
Modern gender affirming "medicine" is NOT science, it's a social phenomenon that has grown out of a very, very sick society that fetishizes minority and vulnerability status, instead of promoting youth, fitness and vitality.
Remain polite, but keep the pressure on. No need for invectives, no need for slobbering at the mouth grug anger. Trust me, coldness and determination are far more fearsome than fits of rage.