To show how truly embarrassing and inexcusable it is for anyone to still deny that the North Vietnamese imposed a reign of terror after they won, let us consider the open letter that numerous former anti-war activists sent to the Hanoi regime in 1979.
To their credit, a number of liberals who played roles in the anti-war movement during the Vietnam War condemned the Hanoi regime in 1979 when they finally--some would say belatedly--became convinced that the Communists were brutalizing and oppressing the people, especially people in the south.
In an “Open Letter to the Socialist Republic of Vietnam” published in five major newspapers on May 30, 1979, Joan Baez and other former anti-war activists called out Vietnam's Communist leaders for serious human rights violations. The letter was written by Joan Baez and Ginetta Sagan and was signed by numerous other prominent liberal anti-war activists, including Norman Cousins, I. F. Stone, Norman Lear, Cesar Chavez, Edward Asner, and Daniel Berrigan.
Guess which anti-war activists condemned the letter or declined to comment on it? Shamefully, the list is very long. A small sampling: Jane Fonda, Dave Dellinger, Abbie Hoffman, William Kuntsler, and Tom Hayden condemned the letter--they actually blamed the U.S. for the oppression in Vietnam (some anti-war activists even argued that the CIA was behind the voluminous refugee accounts). Musician John Lennon and his wife Yoki Ono and actors Donald Sutherland, Michael Alaimo, and Peter Boyle declined to comment on the letter. Vietnam Veterans Against the War leaders John Kerry, Ron Kovic, Jan Barry, and Al Hubbard also declined to comment on the letter.
Of course, Kerry, Fonda, Hayden, and their ilk had specifically assured everyone that Communist rule would not include large-scale executions, concentration camps, widespread oppression, etc. In one TV debate, Kerry said that only a few thousand radical anti-communists would be killed if North Vietnam won. Indeed, some of them even said that Communist rule in the south would actually be an improvement over Saigon's rule.
Perhaps these delusional, false assurances were the reason Joan Baez later complained that she had been "used" by the Left during the Vietnam War.
To her further great credit, Joan Baez led the effort to persuade President Jimmy Carter to help the Vietnamese boat people and other Vietnamese who were fleeing from the Hanoi regime's tyranny. She eventually persuaded President Carter to send the Seventh Fleet to rescue the boat people who were still at sea.
Baez became convinced that the growing mountain of accounts of Communist brutality in Vietnam, especially in southern Vietnam, were true when her good friend and Amnesty International official Ginetta Sagan personally interviewed numerous Vietnamese refugees (see
https://scholars.unh.edu/cgi/viewcontent.cgi?article=1152&context=dissertation). Baez and Sagan teamed up to form Humanitas, which sponsored the open letter. Here is a portion of the open letter:
Thousands of innocent Vietnamese, many whose only «crimes» are those of conscience, are being arrested, detained and tortured in prisons and re-education camps. Instead of bringing hope and reconciliation to war-torn Vietnam, your government has created a painful nightmare that overshadows significant progress achieved in many areas of Vietnamese society. . . .
We have heard the horror stories from the people of Vietnam from workers and peasants, Catholic nuns and Buddhist priests, from the boat people, the artists and professionals and those who fought alongside the NLF. The jails are overflowing with thousands upon thousands of detainees. People disappear and never return. People are shipped to re-education centers, fed a starvation diet of stale rice, forced to squat bound wrist to ankle, suffocated in connex boxes. People are used as human mine detectors, clearing live mine fields with their hands and feet. For many, life is hell and death is prayed for. . . .
Many victims are men, women and children who supported and fought for the causes of reunification and self-determination; those who as pacifists, members of religious groups, or on moral and philosophic grounds opposed the authoritarian policies of Thieu and Ky; artists and intellectuals whose commitment to creative expression is anathema to the totalitarian policies of your government.
Requests by Amnesty International and others for impartial investigations of prison conditions remain unanswered. Families who inquire about husbands, wives, daughters or sons are ignored. (Open letter to the Socialist Republic of Vietnam by Joan Baez 30. mai 1979)
To get some idea of the shocking scale of North Vietnam's reign of terror in the south, read the research done by Jacqueline Desbarats and Karl D. Jackson in their book
Political Violence in Vietnam: The Dark Side of Liberation. Desbarats and Jackson have also published several articles on the subject in various journals, some of which are available online.
Of course, there are plenty of other sources on the Communists' brutalization and oppression of the South Vietnamese, including books and articles by former Viet Cong officials and by former pro-communist South Vietnamese anti-war activists who managed to flee to America after the war.