Of course gender dysphoria is an illness. To have a mental illness ought to carry no more stigma than to have a physical illness, but that is what it is. If your mental health depends on drastic surgery and hormone treatments, then you are ill. And that is what the doctors prescribe, as surely as they prescribed my surgery, and as surely as they still prescribe my drugs, which are mostly painkillers. Otherwise, why should the NHS pay for it? But that treatment does not make you a person of the opposite sex. Of course it doesn't.