Adolph Hitler, whatever else he was, was one of history’s most successful politicians, and he did it primarily on the basis of being an incredibly successful liar. On a number of occasions, the first one two years before he became Chancellor of Germany, he ennunciated forms of his primary rule. Summing these quotations up, what he said was “If you tell a big enough lie, keep it simple, and repeat it clearly enough times, people will believe it”.
He had theories as to why this worked, but I won’t go into them here.
Suffice it to say that Hitler was quite right. If you look for them in the world today, and in recent history, you will find numerous examples of Hitler’s rule in action, although the majority of its users do not apply it so cold-bloodedly, or with such vicious intent. Indeed, many of them go to the trouble of first persuading themselves that what they are saying is true.
The beliefs people hold about why some subsets of society are so poor—they are lazy and shiftless, and their health is poor because they don’t observe principles of hygiene—are probably partly outcomes of the application of Hitler’s rule. Another example would probably be the obviously false belief that it is good for average citizens for a few others to earn literally thousands of times as much as they do for their labour.
As I said, look around you; I’m sure you will find plenty of other examples.