If Mr. Kelly is supposed to be the administration’s disciplinarian, keeping it on message, then echoing his boss’s kind words for slaveholders and those who slaughtered American soldiers to defend them shows that a central message is, “Racists, we’re your guys.”

To Mr. Kelly — and to the White House press secretary, Sarah Huckabee Sanders, who echoed his view from the people’s podium in the briefing room — the Civil War resulted from a failure to compromise. It might be instructive for reporters to continue to press both of them, as well as the president, about what kind of compromise over slavery they have in mind.

The consequences of slavery continue to distort and stunt lives in America, so it’s quite right that we should engage in what can be an agonizing national conversation about this history. Only when our history is faced squarely can removing Confederate monuments be properly understood, as a small but significant step toward ending the celebration of treason and white supremacy, if not toward ameliorating their effects.

But this White House is not interested in that conversation. It’s interested instead in exploiting racist myths and deepening racial divisions for perceived political advantage.

This has been Donald Trump’s only consistent theme since he began building a political base around birtherism. Mr. Trump’s course has been erratic in most respects, but one can draw a sharp, clean line from his lie that Barack Obama was not born in the United States to his calculated attack from the White House on black National Football League players protesting injustice by kneeling during the national anthem. (“Get that son of a bitch off the field right now,” the president of the United States said at a political rally, giving advice to team owners.)

Mr. Kelly had a reputation as a man of honor. Only in the context of Mr. Trump’s toxic political strategy can one understand his attack on an African-American representative, Frederica Wilson, whom he accused of grandstanding — and his continued refusal to acknowledge the truth even after video evidence flatly contradicted him.

It is a sorry development that even Mr. Kelly, a retired four-star Marine general, a former leader of one of our nation’s most racially diverse institutions, is choosing to sacrifice his own reputation to abet the president’s race-baiting.