kallipolis
Know thyself
Much of the empire was established defensively, by taking it away from prior conquerers. Canada and some islands from the French, India from the French, Moguls, Dutch and Portuguese, etc. None of the countries were democracies and many of the native tribal leaders were cruel to an extent far more cruel than the British. Read Alan Moorhead's "The White Nile", history of the search for the source of the Nile by British explorers, and their efforts to end the slave traffic. In the balance, the people of the empire territories were and are better off for the empire.
Your observations are correct....for we Greeks understand, when quoting the Constitution of Athens (between 330 and 322 BC.), and recalling the much respected Pericles, some 70 pct of the population of Athens were "property" i.e. slaves...different times, and different understandings.

