“Selling the Lie” means to deceive or cheat or to create the ‘illusion of truth’. The advertising industry has perfected this rather dark art, using it for the past 100 years, and then “spin doctors” (public relations professionals) of the 70s taught Politicians how to use this form of deception and it was quickly embraced.
Now it has become so pervasive in common that people speak of “your truth” and “my truth” as if there can actually be different “truths”. This is having a catastrophic effect on society and on the individual, which can only further deepen the current mental health calamity. If we cannot accept that there is really an objective reality and think instead that we can (with our imagination) “create” our own truth, then we really are in crisis.