@Vol_Doc since apparently I quoted the wrong post this morning.
So, finally get back to this because I respect you enough to comment.
Now, we are talking something that, by definition, is a genetic issue that the person has zero control over. You're a doctor and you know such things can and will happen from time to time. As to which bathroom to use, that's a tricky question. However, completely and entirely different from "I'm a man who thinks I'm a woman hence, I use the wrong bathroom." However, you divert away from the point I'm making because you know you're about to get this:
Yes, trans-gender-ism is a mental issue. Used to be (and still is to a great extent) a person thought they were something they were not, the King of England for example, they would get mental health treatment for such an issue. It could have been extreme and the person could be declared mentally unstable if the treatments were unsuccessful and the person was a threat to themselves or others. Because it can be easily proven the person is not what they claim, either by scientific method or common sense. "No, you aren't the King of England and we can prove that..."
But a person thinking they are another gender entirely? Hold your horses, that's normal! Umm, WTF. How is that any different from the above situation? Again, we are talking a mental leap of imagination to believe you are something you are not. I.E. a person believes themselves to be the opposite gender when, in reality and can be scientifically proven, they are not. How is this not a mental issue? We aren't talking a genetic abnormality here where the person didn't have a choice. We are talking a state of mind in which a person is rejecting fact for their own mental fiction.
And this isn't the classic definition of a mental illness? If you as a doctor had a patient come in and say "I believe I'm a Sherman tank!" and started walking around the room making engine sounds and knocking over inanimate objects, you'd obviously and correctly ask for assistance from your mental health folks because you believe the person to be mentally ill. However, if a woman with all the correct lady parts comes in and says "I believe I'm really a man." this person is "helped" by medical professionals in stringing that belief along? How is that any different since you can prove it to be untrue? You know the first person isn't a Sherman tank because you can prove it. You also know the person isn't a man since, again, you can prove it. But the situations are suddenly different because of...what?
Change my mind.