James Fallows loved President Obama’s Selma speech: Listening with an “overwhelming reaction of gratitude,” he heard “for once, a public figure expressing exactly how I feel” about the idea of America. Obama’s declaration that “America is not yet finished,” his claim that “we are strong enough to be self-critical,” his insistence that loving America means “more than singing its praises or avoiding uncomfortable truths”—all captured “with concise complexity,” Fallows writes, “what is indeed exceptional about this American experiment.”

It was indeed a fine speech, and a fortunately timed one. Obama took the opportunity to address the Justice Department’s new report on policing practices in Ferguson, which calls out for acknowledgement and comment. And he also replied elegantly to the recent spate of crude, ethnocentric accusations that he rejects exceptionalism, doesn’t love the country of which he is President, and is generally un-American. (These attacks, combined with the sudden uptick of national media interest in Iowa, are a sign that the GOP primary campaign is well underway.) In its coverage of the speech, The New York Times mentioned Obama’s response to these smears: “He did take the opportunity to implicitly fire back at Rudolph W. Giuliani, the former New York mayor, who recently questioned his patriotism.”

This mention of Giuliani’s comments seems slightly out of place in an article about an event otherwise marked by its deep dignity. Because Giuliani is a clown, his attack feels like a joke, and it’s hard to think of such partisan snits as dignified civic exercises of the same caliber as the events being commemorated.

At any rate, it would be easy to adopt that dismissive attitude about these recent attacks on Obama. But I think Saturday’s speech shows why we should guard against that reaction. The right-wing perversion of “exceptionalism”—twisting a self-reflective, morally demanding notion into shallow chauvinism—is more dangerous than most people realize. This is not merely a matter of rhetoric. It directly concerns the way we describe ourselves, the stories we tell about our history. These stories become the beliefs which guide our action.

That’s why it matters that even though Obama celebrated a familiar litany of names and events, he was still careful to insist that the civil rights movement’s victories were not “preordained,” and that America is “not yet finished.” It makes all the difference in the world to see America as an unfulfilled promise rather than a melodramatic unfolding of predestined triumph. Politicians love the latter formulation because it rewrites our worst sins as inevitable victories. Revisions of America’s race history are the most common example (think of Michele Bachmann’s insistence that the Founders “worked tirelessly” to end slavery). Statements like this don’t exist to accurately capture our national experience: They exist to de-politicize it. They transform Americans who were bitterly divisive in their own day—especially Lincoln and King—into banal figures who, stripped of any controversial message, are fit to be appropriated by everybody. People who were divisive in their own lifetimes become objects of hollow universal admiration, and America’s history of struggle and fracture is rewritten as a feel-good melodrama marked above all by a noble consensus.

Fallows briefly notes this point, writing that “these days Martin Luther King Jr. is quoted respectfully even at right-wing gatherings.” But he doesn’t go on to point out the serious problem with King’s saintlike status: As with Lincoln, it has come at the cost of depriving our political discourse of much of his wisdom. King’s message was divisive because it challenged a status quo that many Americans were quite happy with—indeed, were willing to kill in order to preserve, just as they had been with slavery. The assault on that system was divisive, not platitudinal, and many of King’s ideas would still, to this day, prove deeply unpopular at right-wing gatherings, respectful quotations notwithstanding. It is possible to genuinely admire King, Lincoln, and similar figures for the challenging, controversial things they actually believed and accomplished. But this commits us to a slow, difficult politics of disagreement and conflict, because their work had (and still has) powerful opponents. This is not the kind of admiration offered in most American political rhetoric, which instead dilutes the demanding exceptionalism of Lincoln and King until it can do little more than inspire smug self-satisfaction. Obama’s speech was a small step on the march away from that tempting path. Let’s hope it continues.