WHEN the budding pundit Walter Lippmann coined the term ”stereotype” back in 1922, he offered several examples from the America of his time: ”Agitator.” ”Intellectual.” ”South European.” ”From the Back Bay.” You know, he told the reader, when a glimpse and a word or two create a full mental picture of a whole group of people. As in ”plutocrat.” Or ”foreigner.” Or ”Harvard man.”