The 'father' of sociology (sorry, it wasn't Emile Durkheim) wrote this about the nature of knowledge:
"Consider then the relative levels of the different societies and do not deny the truth of a recorded even merely because you have not come across its counterpart in your own age and field of experience. You would be merely constricting your gullet when pecking at the grains of truth!"
Also, some ancient advice for those who engage in the sort of crude and vicious nationalism that passes for patriotism in America:
"One who knows only an inferior or medium form of society should not think it comprises all possible forms and potentialities."