Perhaps I was a little hasty in saying “all” - there were lies that were repeated so often that they became absorbed into some people’s stereotypes - remember the “sideways vagina” thread? Apartheid South Africa and Nazi Germany were particularly adept at this sort of propaganda.
But I would stand by a claim that most stereotypes originate in an experience based on a limited selection of people who share some characteristic which is then assumed to be true of all people who share that characteristic.
From this article dealing specifically with Jewish stereotypes, but I think the comments are generally applicable.
Grim