May be the biggest lie is when capitalism defenders contest that the present system is driving Earth and Humanity to an ecological disaster.
Strangely, the first thinkers of free exchange did not believe that the system was perfect and self sustaining. Adam Smith himself thought that only divine providence could make the system work.
And it has been said that, in fact, he was not a religious man.
Another one : the propaganda of the founders of USSR.
I don’t say Marx and the theoreticians of Marxism who believed what they were preaching.