The only positive thing I can say about Ken Burns’ documentary on the Vietnam War is this — if it is the best the left has, we may blessedly have heard the last of them. The arguments Mr. Burns presents are weak, biased, and insulting. The documentary is scripted to evoke sorrow and moral indignation over what was presented as American error, ineptness, and lack of moral purpose.

The narrative counterposes happy and earnest winners (the communists) with sad and angst-ridden losers (America and the South Vietnamese). It deemed only such perspectives worthy of inclusion. Mr. Burns fails to find even one American or South Vietnamese veteran who wholly supported the war, was proud to have appeared in arms, and sickened by the United States’ abandonment of its freedom-seeking ally.

There are literally hundreds of thousands of us.

No doubt, too, there were North Vietnamese who are critical of the brutality of the communist conduct of the war, but Mr. Burns can’t find them either. We have no way of knowing whether the happy and earnest communist veterans who did appear in the documentary participated in the war crimes — the execution of thousands of civilians — in Hue or any of the countless acts of North Vietnamese-sponsored terrorism.

The Burns documentary accepts without question five pillars of the liberal view of the war:

1. There was moral equivalency between the U.S. and Communist forces, and the goals and objectives of the respective governments.

No there wasn’t. Communist North Vietnam invaded a South Vietnam striving for democracy. The South Vietnamese posed no threat to the North other than by their example. The North had no inherent right to conquer South Vietnam, and the South Vietnamese had no obligation to “vote themselves communist” in 1955. The aberration of My Lai was not “morally equivalent” to the slaughter of civilians carried out by the communists, as a matter of policy, throughout the war. That Americans are better than communists is a point that the left just cannot accept.

2. President Johnson and General Westmoreland accomplished nothing.

American strategy in the first half of the war might not have been perfect. Our strategy of limited war was ill-advised. In the context of the Cold War fears of nuclear war and Communist Chinese intervention a la Korea in 1950, though, it was not without a rationale. By 1968, moreover, the communists were so weakened and desperate they initiated a suicidal attack against the South — the Tet Offensive — and were obliterated. After Tet, the military outcome of the war was no longer in doubt. President Nixon was able to use the favorable facts on the ground that Westmoreland achieved to withdraw all U.S. combat units from the theater and, by unleashing our air power, to bring the communists to their knees.

3. The wars waged in Laos and Cambodia are irrelevant and were just part of the “civil war” in South Vietnam.

When liberals scoff at the “domino theory” it is another reminder of how America-bashing bias obviates reality. North Vietnamese forces — and by extension the Soviets and Chinese communists — were involved in all the region. Both Laos and Cambodia fell to communist domination after America abandoned its ally, with dreadful results.

4. South Vietnam was so corrupt that the North was a viable alternative.

Is there anyone who witnessed communism in the 20th century who believes that? Countless millions have died for the sin of being ruled by reds. Ho Chi Minh slaughtered at least 50,000 of his citizens within weeks of his self-appointment to be ruler of North Vietnam. Their sin? They were educated. They were doctors, lawyers, professionals. They had expressed doubt in the communist government. Every communist leader begins his reign much the same way.

It is typical liberal paternalism — bordering on racism — to attribute to the South Vietnamese people so little intelligence and so much indifference that they are deemed not worthy of wanting and deserving freedom. This viewpoint takes it for granted that the democratically elected Diem administration in Saigon was so evil that rule by Ho Chi Minh would have to be an improvement. The communists called Diem an American puppet, and the Washington establishment was annoyed that he wouldn’t do what he was told. In fact Diem was the elected leader of a free republic. Once America was complicit in his murder in 1963, we assumed a moral duty to see to it that South Vietnam remained free.

5. America was not and has never been exceptional.

Ultimately this is what Mr. Burns would have one believe. That America never does anything based on Judeo-Christian principles. That Americans are never willing to sacrifice anything to give someone else something. That it would be silly to believe that thousands of young Americans sacrificed their lives simply doing the right, the moral thing, by going to the defense of a people trying to govern themselves. That since our founding the American people have never been animated by our founding documents. And that President Kennedy didn’t believe in the imperative to defend freedom and stop communism.

Mr. Burns is wrong in every instance.

Nor is the war hard to understand. The French asked for our help to save their Indochina colony after their 1954 defeat at Dien Bien Phu. We refused. Ho Chi Minh erected a typical communist dictatorship. He was the kind of a nationalist who slaughters his own people and governs with force. So about a million North Vietnamese fled south to Free Vietnam before America became involved in the war. Yet never during the next bloody 20 years did anyone from South Vietnam flee to the north. Never. None.

The U.S. sent advisors. The communists received arms from China and Russia. The war escalated. We sent tens of thousands of combat troops, beginning with the Marines in 1965. The war dragged on, but the communists could not win a significant battle. The Chinese and Russian “uncles” began to tire of the cost and loss of face and pressured the North to open peace talks. Hanoi begged for and received a last ditch supply (enough to outfit multiple battalions of communist troops).

Convincing themselves that the southerners would rally to their side when they overwhelmed the cities and villages in South Vietnam, the North Vietnamese launched a suicidal attack on 100 towns. They were soundly defeated in every one of them in under a week, save Hue (the royal capital) where they held off the South Vietnamese and U.S. Marines long enough to slaughter thousands of the Hue citizens before being beaten back into the jungle. The Viet Cong, more or less the local boys and comprising most of the 50,000 communist troops lost in Tet, were decimated.

Management of the war changed after Tet. Although the American press decided we were losing and began lobbying the public to get out of the war, the military began a four-year pummeling of communist troops. Nixon, elected to stop the war, pulled American combat units out of South Vietnam and simultaneously unleashed U.S. air power, including bombing sanctuaries in Cambodia and the Hai Phong harbor in North Vietnam.

By the fall of 1972, the communists were depleted of morale and arms. Agreeing to a peace conference, they nevertheless tested Nixon by attacking South Vietnamese villages in contradiction of the peace process. Nixon responded with the Christmas Bombing of North Vietnam. Ridiculously referred to as a criminal act akin to the Holocaust and Hiroshima (it killed less than half the number of people killed at the World Trade Center on 9/11), the bombing of the north convinced the communists that they were helpless against the full strength of the American military.

A month later, in January 1973, the North Vietnamese signed the Paris Peace Treaty. At that time, South Vietnam enjoyed a democratically elected government. American combat forces were gone. American POWs were set free. America promised South Vietnam that we would come to its aid if North Vietnam violated the agreement. It looked a lot like victory.

However, the North Vietnamese had not one particle, not one gluon of an intention of adhering to the treaty. They staged increasingly strong attacks in South Vietnam and, while the United States did nothing, were re-armed by Moscow and attacked and overran South Vietnam. The American Congress, controlled by Nixon’s opponents in the Democratic Party, which had driven him from the White House, voted to renege on our treaty obligations and cut aid to our South Vietnamese allies.

They forfeited outright the peace for which almost 60,000 Americans and hundreds of thousands of South Vietnamese fought and died. They accepted no responsibility for the atrocities that followed.

It is the raison d’être of Mr. Burns’ film to justify the cowardly and morally bankrupt left that supported the communist invasion of South Vietnam and turned its back on the murder, imprisonment, and misery of our former allies in Vietnam, Laos, and Cambodia. One cannot be against the South Vietnamese without being for the communists who conquered and enslaved 17 million people. Only by painting the war as immoral, illegal, and un-winnable, and the South Vietnamese government as evil and inept, can the American left hope to rest in peace. It shouldn’t bet the farm on that.

Mr. Jennings is the author of, among other books, “The Politically Incorrect Guide to the Vietnam War.”