Your older white male coworker Steve comes running into the office, clearly agitated. He reports breathlessly, "There's a bunch of dudes with katanas fighting in the parking lot!" This, you think, is a thing worth seeing in addition to being cause for some alarm. You rush over to the window and discover that the parking lot is empty. "Steve," you say, "where did they go?"
"What do you mean, where did they go? They're right there! Look at them!"
To reassure yourself (and hopefully Steve) that you have not somehow overlooked this scene which on its face seems unlikely to be overlooked, you check the parking lot one last time. Cars, yes. Another coworker strolling into the building, yes. The parking attendant, yes. Two pigeons, yes. But no men fighting with katanas. In fact, neither men nor katanas are anywhere to be found. "Do you mean to tell me that you can't see that there is no one in that parking lot, Steve?"
He grows angry. "THEY'RE OUT THERE, I'M TELLING YOU."
How concerned would you be about Steve's mental state at this point? You might think he's in the midst of a cardiovascular event that is limiting the flow of oxygen to his brain. You might wonder if he is drunk or high on drugs. Or you might think, and not entirely without justification, that he is having some kind of psychotic break. And if you told your boss and other coworkers what happened, they would agree with you without hesitation that he is acting nuts and you are right to be concerned. Collectively, you would probably call the hospital or his doctor, or at least have someone drive him home. I mean, you wouldn't let someone drive a car after witnessing that kind of inability to integrate the world around him into his thinking. You certainly wouldn't just ignore all of this and let everyone go about their day.
So when an older white male tells a room full of other older white males in a nationally broadcast forum that Muslims have taken over a number of cities including Dearborn, MI and established "no go zones" wherein Sharia law is practiced, why does nobody check if perhaps his collar is a bit too tight? Why doesn't anyone sit him down and offer him a nice cold glass of water while someone else calls for medical help? Insisting on the existence of something that demonstrably does not exist – and remember, this is hardly the kind of thing that could be hidden from view as most conspiracy theories can conveniently claim – is neither a fact, nor a belief, nor an opinion. It is a delusion, defined as "an erroneous belief held despite strong, indisputable evidence to the contrary." Delusions are a sign of, at best, mental fatigue or confusion. In most cases they are an indicator of something much more serious.
It is only because so many people in this country believe things that are demonstrably, incontrovertibly wrong that we do not find this more alarming. We've simply become used to it and we hardly flinch when we see True Believers, with the fires of sincerity burning in their eyes, insisting that whatever fantasy occupies the far right at the moment is true. It is odd that labeling these delusions as part of our political or religious beliefs inoculates them from the kind of reaction they would get if "Muslims" was replaced with "unicorns."