When someone is called "a schizophrenic," this strikes me as derogatory. It implies you are not really a person, but rather, you are an individual defined by a disease. The word is an adjective. In other words, I am "someone with a schizophrenic illness." If someone were in treatment for cancer, you would not refer to that person as "a tumor," or as, "a breast cancer." It might not seem like the same thing to you, but really, it is the same thing. "He was schizophrenic"... In that sentence, the word is used as an adjective, and it is used to describe a person's state, without calling him names. "He was a schizophrenic"... In the second instance, simply by adding the word "a," you are in the zone of name-calling.
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