People are, and have always been, able to persuade themselves to believe the weirdest things. If a theory is not testable then it is either rejected or it becomes a matter of belief, which people can be readily persuaded to accept and even proclaim with varying degrees of conviction. Economic theory is by no means unique in this.
A hundred years ago, there being no tv, cinema or even radio, people tended to socialise mostly face to face with real people. And even in godless England, much of that interaction was within the context of the Christian church. Children attended Sunday school, went on Sunday school treats and outings, and in due course were confirmed as church members and regularly attended its services. That was where girls and boys very often met up. In the absence of mass hi-tech entertainments, they joined church youth clubs, played sports for church teams, contributed to church concert parties and drama societies, participating in, and being entertained by, their various amateur productions. As a consequence they were imbued with a set of values which were essentially benign and had some influence over how people behaved to each other. Fairness, honesty and generosity were at the core of those values and were publicly proclaimed, far beyond the church, as the acceptable way to behave. It didn’t mean people believed all the detail the churches promulgated. They didn’t have to. Christian doctrine was a matter for theologians. The mass of people were not overly exercised about the details of belief.
Fighting for Fairness by Remaking the Real Economy 