Most of human history is the history of elites, of kings, queens, princes, prelates, magistrates, potentates, knights, earls, and squires, all of whom subordinated and exploited everyday people.
It makes it seem that exploitation of people are normal and occurs almost with history and seems to be something that minorities or less favorited race occurs too. The author is basically using precedented knowledge to make their point that this has occurred for awhile and its time to change it.