Donald Trump has never, as far as anyone knows, been diagnosed with a mental illness by any professional who has first-hand personal experience, although there is a lot of armchair diagnosis currently being done by professionals. It’s understandable, given some of the erratic behavior Trump exhibits, but Trump has engaged in such behavior for a long time now. (One of the more bizarre stories that emerged during the campaign was about Trump using fake names such as “John Barron” to talk to the media about himself. And then there is the years-long birther controversy and the latching on to other strange conspiracy theories.)

Trump is not mentally ill, as far as I can see has been reliably stated by a professional who has examined him in person. No, Trump is a liar.

The difference matters.

There is a tendency in this country to label any behavior that lies outside what most of us think of as the generally accepted norms as being mentally ill. Guy shoots up a workplace? He must be mentally ill, ignoring the fact that he had a history of workplace violence and the victims had gone to management to complain. Guy shoots up a church full of black people? Must be mentally ill, ignoring the fact that he was a stone-cold white supremacist.

The president lies repeatedly about things both large and small, even where his lies undercut American democracy and our standing in the world?

Must be mentally ill, ignoring the support the man will get from the third of the country who both believe and support him. Must be suffering from dementia, ignoring the lengths the man will go to for political ends.

What of his supporters? Many of Trump’s lies are not only false but laughably, demonstrably false. Are they mentally ill, too? Are they suffering from impaired cognition?

To view Trump and his supporters as mentally ill reduces the moral responsibility they carry. If Trump is mentally ill, those damaging tweets are the product of a diseased mind, not the opinions of a political and governmental neophyte who is in way over his head but who is nonetheless willing to destroy anyone he sees as standing in his way. If he is falling into dementia, those offensive comments come from cognitive decline, not from a carefully tended sense of social superiority over everyone in the world, created by an upbringing in which no one ever told him no.

A lot of people engage in such destruction, albeit on a smaller scale: abusive bosses, violent spouses. Like such people, Trump refuses to allow people to say no to him safely. Exhibit 1: regardless of the damage Trump’s tweets do to his image, he still shows up on Twitter. I don’t know for sure, but I seriously doubt his people in the White House have not tried to take the Twitter account away from him. Exhibit 2: Trump’s habit of publicly savaging people who don’t do exactly what he wants (see: Jeff Sessions, Rex Tillerson).

Identifying Trump as mentally ill simply increases the stigma that the mentally ill have to deal with.  Having a mental illness sucks enough already; we don’t need unwarranted comparisons to Donald Trump.