The great man was moving with what seemed like great reluctance. He knew as he climbed from the car in Upper Manhattan that he was stepping into the maelstrom, that there were powerful people who would not react kindly to what he had to say.

“I come to this magnificent house of worship tonight,” said the Rev. Dr. Martin Luther King Jr., “because my conscience leaves me no other choice.”

This was on the evening of April 4, 1967, almost exactly 43 years ago. Dr. King told the more than 3,000 people who had crowded into Riverside Church that silence in the face of the horror that was taking place in Vietnam amounted to a “betrayal.”

He spoke of both the carnage in the war zone and the toll the war was taking here in the United States. The speech comes to mind now for two reasons: A Tavis Smiley documentary currently airing on PBS revisits the controversy set off by Dr. King’s indictment of “the madness of Vietnam.” And recent news reports show ever-increasing evidence that we have ensnared ourselves in a mad and tragic venture in Afghanistan.

Dr. King spoke of how, in Vietnam, the United States increased its commitment of troops “in support of governments which were singularly corrupt, inept, and without popular support.”

It’s strange, indeed, to read those words more than four decades later as we are increasing our commitment of troops in Afghanistan to fight in support of Hamid Karzai, who remains in power after an election that the world knows was riddled with fraud and whose government is one of the most corrupt and inept on the planet.

If Mr. Karzai is at all grateful for this support, he has a very peculiar way of showing it. He has ignored pleas from President Obama and others to take meaningful steps to rein in the rampant corruption. His brother, Ahmed Wali Karzai, the kingpin in southern Afghanistan, is believed by top American officials to be engaged in all manner of nefarious activities, including money-laundering and involvement in the flourishing opium trade.

Hamid Karzai himself pulled off a calculated insult to the U.S. by inviting Iran’s Mahmoud Ahmadinejad to the presidential palace in Kabul, where Ahmadinejad promptly delivered a fiery anti-American speech. As Dexter Filkins and Mark Landler reported in The Times this week: “Even as Mr. Obama pours tens of thousands of additional American troops into the country to help defend Mr. Karzai’s government, Mr. Karzai now often voices the view that his interests and the United States’ no longer coincide.”

Is this what American service members are dying for in Afghanistan? Can you imagine giving up your life, or your child’s life, for that crowd?

In his speech, Dr. King spoke about the damage the Vietnam War was doing to America’s war on poverty, and the way it was undermining other important domestic initiatives. What he wanted from the U.S. was not warfare overseas but a renewed commitment to economic and social justice at home. As he put it: “A nation that continues year after year to spend more money on military defense than on programs of social uplift is approaching spiritual death.”

The speech set loose a hurricane of criticism. Even the N.A.A.C.P. complained that Dr. King should stick to what it perceived as his area of expertise, civil rights. The New York Times headlined its editorial on the speech, “Dr. King’s Error.”

Mr. Smiley, in his documentary, noted that “the already strained relationship between President Johnson and Dr. King became fractured beyond repair.” And donations to Dr. King’s Southern Christian Leadership Conference “began to dry up.”

So it took great courage for Dr. King to speak out as he did.

His bold stand seems all the more striking in today’s atmosphere, in which moral courage among the very prominent — the kind of courage that carries real risk — seems mostly to have disappeared.

More than 4,000 Americans have died in Iraq and more than 1,000 in Afghanistan, where the Obama administration has chosen to escalate rather than to begin a careful withdrawal. Those two wars, as the Nobel laureate Joseph Stiglitz and his colleague Linda Bilmes have told us, will ultimately cost us more than $3 trillion.

And yet the voices in search of peace, in search of an end to the “madness,” in search of the nation-building so desperately needed here in the United States, are feeble indeed.

Dr. King would be assassinated exactly one year (almost to the hour) after his great speech at Riverside Church. It’s the same terrible fate that awaits some of the American forces, most of them very young, that we continue to send into the quagmire in Afghanistan.