It reminds me of the way fat people are treated actually; in both cases, the “normal” person has experience with eating food and occasionally being acutely depressed. But they have no experience with the other side of the equation, and assume both are caused by some sort of lack of character or willpower on the part of the fat/depressed/mentally ill person.
Basically what they do is take their experiences with it, and extrapolate what it would take for them to be in that same situation(sort of a reverse “in the other’s shoes”), which points to some sort of negative personality trait like laziness, no self control, selfishness, wallowing in self pity, etc…
But it doesn’t work like that.