If your lie is going to be propagated, not only are you going to have to override people's reasoning, but you're going to have to give them a reason for doing it. While you're at it, it may help to appeal to people's basic social needs. Mankind is a social animal. And then you'll need a propagation piece to tie things together. So maybe you'd start with fear.
Fear is one of man's most primitive and powerful emotions, related to self-preservation.
You would want people to believe that if they didn't accept your lie, something really horrible would happen to them. You might further convince them that so much as questioning your lie would have disasterous consequences. Next, appeal to people's insecurities and justify their negative emotions. Without your lie, they have no hope. They're not worthy of happiness or acceptance if they don't believe you.