The strategy is as old as the hills.
Show people an extreme example of something, and thereby convince them to accept a compromise.
In this case, parade before the public—along with assured pronouncements from “mental health experts”—images of James Holmes, Aaron Alexis, Adam Lanza, etc.—and say:
“Look, these are people who committed unspeakable crimes because they were suffering from mental disorders, and we must do something about it…in fact, at least half of all Americans have some sort of mental disorder…”
It’s a nudge, a coax, a veiled threat, an invocation of fear.
“Gee, maybe I have a mental disorder and I don’t even know it.”
It softens up the population.