President Obama, standing in front of the American and Communist flags, announced in Hanoi this week that he’s ending the embargo that has for 50 years blocked US arms sales to Vietnam. The move, he said, would end a “lingering vestige of the Cold War.”

Between North Korea, Red China, Cuba and Vietnam, it’s a bit of a trick telling one lingering vestige from another. How about the lingering vestige of the Communist Party? When are we going to end that?

It’s not my intention here to re-litigate the Vietnam War. (In my opinion, history will vindicate the hawks and go hard on the Congress, where America’s hard-earned battlefield victory was given away in pursuit of an illusory peace.)

Yet it’s just bizarre that Mr. Obama and Secretary of State Kerry seem to think that our embargo was more of a problem than the Communism itself. Even if Red China is itching for a war in the South China Sea.

Arms to Vietnam have a certain logic. It’s like Winston Churchill saying, when the Nazis entered Stalin’s Russia, that if Hitler invaded Hell he’d at least make a favorable reference to the Devil in the House of Commons.

In Southeast Asia the theory is that the Communists in China are more of a threat to American interests than the Communists in Vietnam, China’s traditional foe. Yet President Obama is denying that the end of the arms embargo is linked to China.

It was, Mr. Obama insisted, based on “our desire to complete what has been a lengthy process of moving towards normalization with Vietnam.” But he has brushed aside all sorts of red flags about the nature of the regime.

Human Rights Watch sent him a letter nearly a month ago, warning of what he was dealing with in Vietnam’s Communist camarilla. It called Vietnam’s government “one of the most repressive in the world.”

It noted that expression, association and assembly are “extremely limited,” that the press is controlled and censored and that the Communist Party “controls all public institutions and uses them to maintain its hold on power.”

Human Rights Watch characterized the elections in Vietnam as “a form of political theater.” The president with whom Mr. Obama has been treating, Tran Dai Quang, it noted, is the thug who headed Vietnam’s “notorious Ministry of Public Security.”

In Hanoi this week, Mr. Obama insisted that any arms deals would have to meet the usual requirements, including human rights. But who believes him after the hash he made of the Iranian appeasement?

Mr. Obama doesn’t seem to grasp that the Communism itself is the human-rights violation. Speaking to students in Argentina two months ago, he brushed off the distinction between capitalism and Communism as “interesting intellectual arguments.”

“Just choose from what works,” Mr. Obama said. It was one of the most ridiculous comments of his presidency. If the century since the Bolshevik revolution has taught us anything, it’s that we know which one works.

Even the Communists know. They just don’t know — or care — what makes capitalism work. That’s the comprehension that liberty and prosperity are linked. There’s no difference between economic and political freedom.

Oh, there were fine words when Messrs. Quang and Obama made their toasts in Hanoi. The Vietnamese president quoted the appeal to President Harry Truman from the father of Vietnam’s Communist revolution, Ho Chi Minh.

Ho appealed for American support for independence. America refused in part because Ho Chi Minh was without standing. He had long since become a Communist agent. He had never stood before his people in an election.

The leaders who have done that are to be found in, say, South Korea and the free Chinese republic of Taiwan. They have built prosperous countries, where political parties contend, newspapers cover them, and people can worship God. And come and go.

No doubt China is the bigger strategic threat, but it would be ironic if we arm Vietnam and it goes into a fight with the Chinese. American rockets could be falling on Chinese Communists instead of Chicom rockets falling on Americans.

Then again, our selling arms to Vietnam could well result in the Communist regime there using them against the Vietnamese people, including those in the South to whom we once supplied arms — and gave 58,209 American lives — to secure their lingering vestige of liberty.

This column first appeared in the New York Post.