K8 and I seem top be on the same page.
There is a huge stigma surrounding mental illness. People who have them will often not seek help because they don't want to think that something is seriously wrong with them. People don't like the idea of something being wrong with them. With any other mental illness (depression, schizophrenia, etc.) there are things biologically and chemically effecting the way the brain is working, and it affects emotional and physical well-being. With any mental illness, there are physical symptoms as well. When you have depression, the person can become fatigued, lose their appetite, and gain lots of weight. Those are physical symptoms.
With GID, the physical symptom just happens to be HUGE. The body is the wrong gender. There are also emotional symptoms like dysphoria, anxiety, and depression. GID is a conflict between brain/body identity.
With most other mental illness, the treatment involves therapy and medicine. Most trans people go to therapy and are medicated with hormones, and the final treatment is a full-body transformation. I understand that some people are uncomfortable with thinking that being transgendered is a disorder, but if the treatment involves actually getting the desired body, I don't personally see the problem.