Insanity is a contagious disease that comes into being when there are too many humans to be heard and taken into account. Insanity is the herd mentality; the social condition in which the loudest bark, bellow, bray or bleat sets the tone, and the tone forces the question of whether you're for or against it.
If you're not completely insane, you see the madness and stay out of it. If you're only partially insane, you may believe you can cure insanity. Either way, the madness of society rages on until enough humans have developed immunity to the disease, or the disease decimates the whole species.
What makes an organism immune to its specie's common complaint is unknown, but an organism's immunity makes it of special interest to complainers who are sick of themselves. These complainers, believing that immunity spreads like disease, seek out the apparently immune ones and identify with them until they're convinced they've vanquished their disease. They undergo a make-over. The disease is all about appearances and the inability to see through them, so the cure for the diseased is a new appearance.
Immunity can't be spread or contracted like disease. It's a rare condition. It may have no cause. We think we know it when we see it, but we're easily deceived. All we know is that we believe in it and we want it because we're doomed without it. What we don't know is why or how it comes about and whether there's any hope that the average lunatic might suddenly, inexplicably, find itself immune to the human condition.