Colbert launched his vituperative parody when there was no forum for the president—or anyone speaking on his behalf—to reply. Again, First Amendment doctrine seems relevant: While concepts like "equal time" now seem relics of the Sixties and Seventies, and the FCC long ago junked the "fairness doctrine," we still remain more comfortable with harsh speech when the target has a chance to quickly respond.

All else being equal, the situation would seem especially unfair in First Amendment terms because the brand of irony of which Colbert is a master serves—as Scherer points out, quoting David Foster Wallace—"an almost exclusively negative function" for which there is no easy response.

However, all else is not equal. The president, with his "bully pulpit," has a platform from which to command attention, and a national audience, as no other individual can. If he decides to address the...