He didn't compare mentally ill people to Jason; he said they were treated like Jason. IE someone who isn't a psychotic killer is being treated as if they were.

you aren't very good at reading comprehension if you think that's what he said.

But a lot of people then (fewer now) believed those with mental illness should be treated like Jason Voorhees and gunned down like a rabid animal or locked in an institution and kept tranquilized my the nurses.

you should read this again. And then again, and maybe one more one time just to be sure.

They said that others were treating mentally ill people like psychopaths, not comparing mentally ill people to Jason themselves.