I would be insulted too. I am not a combative person but if someone said I was autistic I would ask: "What medical schools have you attended and received degrees from?"

I hope you will get over the rudeness of these clueless people. My heart goes out to you!

People who read a Wikipedia article or watch an episode of talk TV often feel as though they are qualified to diagnose people or label people with mental health terms.

A recent trend among some psychologists is to question the growing proliferation of derogatory mental health labels.

Too many psychological categories ruins the purpose of having labels since the result will be that everyone is mentally ill. It is like: "You have x psychological disorder, subcategory 2452." Hello!

There is something that few people talk about outside the clinical psychology profession. It is the fact that well-qualified, well-meaning and well-experienced therapists often disagree on a diagnosis. One will say: "You have x." Another might say: "You don't have x, you have y."

Since professionals can disagree on these things, what gives the average person the arrogance to declare that someone has a mental illness?

In the early years of psychology it was a widely held belief that mental illness was ultimately psychological traits that caused a person to be unemployed or unemployable.
The goal of psychotherapy was to enable to person with certain traits and habits to be employable again.

That was where the bar was set. Here's a person experiencing some distress in their life? Can that person, in spite of their distress, still go work day after day. If they couldn't, they were considered mentally ill.

Does any of this prove helpful to you or have I completely missed the points you were making?