They say that what people like him are really suffering from is a form of psychosis called delusions of parasitosis, or DOP. He is, in other words, crazy.

This is one of the problems in our society, even in psychiatry. (The OP deals with the binary nature we apply to such things, but could have gone deeper.) This idea that there are "crazy" people who have all kinds of mental illness, in full cinematic severity, all of the time, and "sane" people who have none isn't accurate. About 30 to 50% of the population will have diagnosable mental illness at some point in life. (We use our brains for so many things; that we'd have problems with them, over an 80-year life, shouldn't surprise anyone.) Likewise, most people with MH diagnoses are normal most of the time. It doesn't define one as a person, any more than heart disease or fibromyalgia does. This parasitosis is shocking people because it's occurring in relatively normal individuals, but that's actually the truth for most of these diseases. Most people with panic attacks or depression don't seem "insane", because (although they have mental illnesses) they're not.

We need to stop thinking of these as alien, stigmatized conditions and start viewing them as "boring" chronic health problems that, while they are painful and deserve compassion and treatment, don't merit treating someone as if his life is already forfeit (like a cancer patient in the 1940s, an AIDS patient in the 1990s, or a schizophrenic in the 2010s). Panic disorder, for one example, is more like a milder version of epilepsy than a typical "mental illness". It doesn't impair judgment or cause delusions; it's just very upsetting and difficult.

Most people with mental illness are mostly sane most of the time. In our society, we tend to focus on the highly visible and extreme cases, not on the "boring" and often treatable ones that are more common. Major depression doesn't mean that a person is always miserable; it means that a person is unusually prone to attacks of negative mood, often unprovoked. You can have MDD and still be happy most (say, 80%) of the time. In fact, quite a large number of people with anxiety and mood disorders are more functional than the general population when unaffected by the disease (which can be anywhere from 30 to 90% of the time; trust me that if you have two weeks of mania and two weeks of major depression per year, you're still bipolar and need help).

“In my experience, Morgellons patients are doing the best they can to make sense of symptoms that are real. These people have been maltreated by the medical establishment. And you’re very welcome to quote me on that. They’re suffering from a chronic itch disorder that’s undiagnosed.”

This seems likely. Even if the disease is "psychological", it's still real pain that they're suffering. I understand that it may require more attention from psychiatrists than dermatologists, but that doesn't invalidate the disease and the importance of treating it.

It can be called enigmatic because it seems (from what I've read) to be psychiatric and is popping up in "normal" people, but the fact is that most mental illnesses (panic, anxiety, depression, OCD) pop up in otherwise normal people.

But, she adds, that is not to say there aren’t some patients whose major problem is psychiatric. Others still might suffer delusions in addition to their undiagnosed neuropathic illness.

I'm not altogether convinced that there's a difference between neurological and psychiatric illnesses. I've often thought that panic disorder is a non-lethal (albeit distressing and sometimes just weird) cousin of epilepsy (generally classified as neurological) and that the "Asperger's syndrome" (neurological) often observed in highly intelligent young people is actually a mild, subclinical cyclothymia (bipolar) disorder. (People with true neurological social disabilities, such as with autism or head injuries, don't grow out of them in their mid-20s; but people with mild bipolar disorders have a social experience deficit that would match that pattern. Being 20% behind at age 15 is catastrophic; at 30, it's quirky; at 40, it's a non issue.)

Anyway, fuck the people who say that a disease being "psychiatric" means that it shouldn't be treated. It reminds me of the claims adjuster in Memento (ignoring issues of unreliable narration and the question of what really happened) who wanted to weasel out of covering treatment for amnesia because it was "psychological".