I believe that the OP is confusing the diagnosis of a mental illness with the assignment of a stigma. A diagnosis is not the stigma; the stigma is the external opinions about the diagnosis.

To me, a 'disorder' is anything that causes distress, discomfort, pain, suffering, etc to an individual (I know that this is not an exact definition of the term). Whether you believe it's personality, biological, neurological, psychological, etc, people still suffer and struggle from mental disorders. That is why many of us are sensitive to being told that what we struggle with doesn't exist or that it's a simple change of mindset to overcome.

People can decide whether or not they will apply the stigma of their diagnosis to themselves. A diagnosis doesn't mean that someone's mind isn't beautiful or that they have to believe they are flawed. Personally, being diagnosed bipolar was a bit liberating to me -- I feel as though I know I have something I legitimately struggle with.