Where you say schizophrenia you probably mean split personality disorder. I am not even bothering to re-read your first sentence because of your perpetuation of this horrendous misuse of language.
Actually you're talking about the medical definition whereas he's using the colloquial definition. I agree that the mismatch is unfortunate and perpetuates stereotypes about the medical definition, but he isn't wrong to use the word like that, according to the dictionaries I've checked.