Blood Libel

A Blood Libel was a common tactic used by medieval groups to justify the oppression of outside groups, usually Jews, it consisted of demonization, propaganda and even violence - often they would focus on stories depicting Jews or Gypsies as evil, child-killing maniacs and encouraged open resentment, fear and even genocide of said groups.

Similar tactics were in use in innumerable dictatorships throughout history and continue to be used by destructive cults and hate-groups.