While I am not a mental health professional I believe they have not only the right but the duty to speak out if they have cause to reasonably believe someone with the capacity to end tens or hundreds of millions of lives in a matter of minutes is suffering from serious mental and emotional deterioration.Ethically, the situation is very complex. Ethics is not the field of finding universally correct moral answers. Ethics is a quest for a useful framework when competing goods need to be weighed against each other. It is not the only framework, but I prefer using the four principles framework:
Beneficence -- helping a patient
Non-maleficence -- not hurting a patient
Autonomy -- respecting a patient's wishes
Justice -- dealing with equity, etc., for the greater system
Here we potentially put non-maleficence and autonomy at odds with justice. There is not a universal right way to weigh things, but generally if you are doing a physician task (diagnosis, treatment recommendations) for someone you have not established care for and not examined and going against their individual interest and choice, it demands a pretty high bar.
My biggest question here is, should any individual or collection of individuals cross that boundary, does it have any positive practical effect? Most of the time we are dealing with unknowns, e.g. you can't predict who will have an infection after surgery, but this doesn't mean you don't use evidence to weigh likely risks and benefits.
It’s much like impeachment. Will it remove him from office? Probably not. That doesn’t absolve the House from its duty.