Philosophy prides itself to be concerned with arguments: finding valid (and preferably sound) arguments, and exposing and rejecting fallacious ones. Ideally a philosopher will form opinions on the basis of good arguments only.
Few are naive enough, of course, to believe that the most successful persuasion happens by rational arguments alone. But maybe we can expect philosophers to be more aware of fallacies and less prone to buying into mere rhetoric? Political debate and advertising could make for two interesting test cases here. Takers?