In my study of communist societies, I came to the conclusion that the purpose of communist propaganda was not to persuade or convince, not to inform, but to humiliate; and therefore, the less it corresponded to reality the better. When people are forced to remain silent when they are being told the most obvious lies, or even worse when they are forced to repeat the lies themselves, they lose once and for all their sense of probity. To assent to obvious lies is...in some small way to become evil oneself.
Having been exposed to some CNN on my recent travels, I kept noticing that the talking heads were proclaiming as plain fact, emphatically and repeatedly, things that were not merely false but glaringly, obviously preposterous. ("A small group of 17-year-old kids spontaneously organized a nationwide protest and chartered a fleet of buses!" Yeah... right.)
But the people inside the magic box keep saying these things, so they must be true. You can't disagree with the people in the magic box! That would be wrongthink!
Then consider the theatrics of today's protests (regardless of the cause nominally being supported). Not much there to persuade those outside the group, is there? It's all about group cohesion... and about getting the group members to engage in humiliating behavior in public (just look at some of those costumes) so that they'll never be able to return to the word outside the Movement.
I need to re-read Lucifer's Hammer. There's a half-remembered description there of how the cannibal cult's members were rendered incapable of rejoining society at large.