He is schizophrenic. One of the defining features of schizophrenia is that they can't be reasoned with. They have periods of complete lucidity followed by periods of complete craziness due to physical deterioration of the brain.

He deserves a good doctor. If we can do anything, then we should set up a fund for medical treatment. He has said that doctors haven't been able to help him, but maybe whoever is caring for him hasn't been able to afford top-tier care. It makes a huge difference.

In practice, setting up such a fund would be difficult because we don't know who's caring for him or how.