Because some people would go insane without having an external authority to appeal to; the extant systems of academia and qualification create an "objective" truth these peoples' psyches can cling to.
https://www.psychiatry.org/patients-families/stigma-and-disc...
it's the same idea as not calling people the 'r' word and why that word itself is no longer used in official diagnoses. it's a boundary condition grounded in compassion. advocating for using a new word doesn't need some soapbox tantrum about the fatuousness of the modern world a la Ignatius J. Reilly
this bloviating about free speech when all anybody is asking you to do is to not be an asshole is so overwrought and childish
The idea that you can "diagnose" someone with a mental illness based on reading their court filings and things they've written online, without ever speaking to them in person, is... well, just bonkers. It's irresponsible, at best.
Someone can exhibit anti-social behaviors without having a mental illness.
This is as frustrating as people I know who are constantly saying "I think so-and-so is autistic/has ADHD". Yes, sometimes it's correct, but often it's not, and the outward symptoms of those two conditions often lead to a true diagnosis of something else entirely.