For the copy editor, the mission of vigilance is often clear-cut. If a story quotes a private citizen using a vulgarity when discussing the employment crunch or MBTA fares or the Red Sox, the copy editor can paraphrase, truncate the quote, or remove the sentence entirely. But the terrain shifts when the speaker is a public official or a candidate for office. Then, editors must balance the desire not to offend with the need to furnish full pictures of our leaders, warts and all.