The principle
The truth is often avoided because it is ugly and unpleasant. Anyone who can promise a glamorous alternative will attract followers regardless of how unrealistic the promise is.
The application
Markets, careers, and movements run on this. The cleanest version is selling people the version of themselves they want to be. The dirtiest version is selling people a version of reality that cannot exist.
The defensive tell — how to spot it being run on you
When something is being sold to you that maps exactly onto a fantasy you already had, slow down. The fit is too convenient. Fantasies fitted by salesmen are designed; the ones fitted by life are uglier and truer.