Paranoid Schizophrenia Ilness or Not?

Symptoms: Delusions are defined as firmly held beliefs that are untrue, not shared by others in the culture, and not easily modifiable.

Well wearing tin foil hats by so called Schizophrenic's is one of the most common things they do, so that is a belief shared by lots of others. So they aren't mentally ill, they are just eccentric.

I am a diagnosed schizophrenic and can tell you that there is something to OPs theory. I never had any attributed symptoms of the like "Hallucinations" or "Hearing voices" but some crazy ass paranoia.
But certainly nothing that couldn't be fixed with some calm talking to someone trustworthy.

Imo it is nothing but behaviour that is deemed unacceptable in society, exploited by big pharma to sell their products which makes it into a treatable "disease".