Imagine that you enter a big-city taxicab and the moment you get settled in, the driver begins a harangue about the supposed iniquities and inferiorities of another ethnic group. Is your best course to keep quiet, bearing in mind that silence conveys assent? Or is it your moral responsibility to argue with him, to express outrage, even to leave the cab—because you know that every silent assent will encourage him next time, and every vigorous dissent will cause him next time to think twice?
