Don't worry about it. He is schizophrenic and believes God talks directly to him. If you had this problem, you probably wouldn't want to take medication for it. He thinks he has been chosen. It really isn't under his control.
I had an uncle with schizophrenia (and a father with much less severe symptoms). You are right that you wouldn't want to take medication for it. To the schizophrenic mind, the benefits of schizophrenia far outweigh the costs -- and besides, you can't really trust anybody else to be either competent enough to medicate you, or to have your best interests in mind when medicating.
