In Hanoi this week, a short-lived exhibition at Vietnam's National History Museum, Land Reform 1946-57, triggered a national moment to relive a long-ago trauma.

On September 5, the Ministry of Culture, Tourism and Sports website posted an announcement saying that the History Museum would hold an exhibit from September 8 until December assembled from the archives of the central government, the Communist Party and various provincial museums. It was an exhibit "pregnant with valuable historical contents never shown before," the ministry said.

Scholars outside Vietnam and (very quietly) inside the country have debated for 60 years how many landlords ‑ large, small, kind, wicked, pro or anti-Communist -- perished in the paroxysm of class warfare that followed France's expulsion from the northern half of Vietnam in 1954.

A few Vietnamese who remember that period intimately, notably the economic historian Dang Phong and, very recently, the journalist Tran Dinh, have said openly that the ideologically driven land reform campaign was a complete failure. For younger generations, however, the gory details ‑ at least 100,000, and perhaps two or three times that many, landlords were shot, beheaded or beaten to death by peasant mobs incited by Party cadres – have been lost from view.

The curators at the National History Museum certainly did not intend to arouse doubts about the correct management of affairs long ago. The exhibit was designed to "educate… especially youth to comprehend more deeply and correctly the agricultural revolution… and strengthen belief and pride in the Party, government and revolutionary achievements of the People." They didn't reckon with the Internet.

As in many other nations, the rowdy online world of news, rumor and rants has hamstrung the regime's effort to manage public opinion. News of the exhibit caused a flood of online claims that it whitewashed the past, triggering long repressed accounts of chaos, cruelty and injustice, meted out even to revolutionary heroes like Nguyen Thi Nam who were, incidentally, also substantial landowners.

Well over a third of Vietnam's 90-plus million people regularly go online, mostly to play games and socialize, but also to read stories that don't get reported by the authorized media. They read, for example, that these days land is often wrested from farmers to clear the way for industrial, commercial or housing projects, and that the courts are clogged with lawsuits protesting the meager compensation given in exchange. It was not a big surprise, therefore, that the unprecedented exhibition prompted grandparents to relate miscarriages of justice during the land reform period and their grandchildren to post them on blogs or Facebook accounts.

Can we come in? On the morning of September 9, the third day of the exhibition, a few dozen people, all wearing red shirts proclaiming themselves farmers from the village of Duong Noi and bearing placards demanding "human rights," marched from a bus station to the History Museum.

They'd come to see the exhibit, they told guards.

The guards had no difficulty, apparently, recognizing the people in the red shirts as farmers who have for two years been protesting the Hanoi City Government's seizure of their land for redevelopment.

"It's 11 am," the guards pointed out. "We're closing for lunch until 2 pm."

At 2 pm, the farmers from Duong Noi were back. "You'll have to take off those red shirts," the guards told them. The farmers complied. The guards conferred again and announced that there was a lighting problem in the museum so the land reform exhibit was temporarily closed.

Inside the building, representatives of the Communist Party's Propaganda Commission and officials of the Ministry of Culture were talking to museum director Nguyen Van Cuong. Presently it was announced that the land reform exhibition would be closed and replaced by an exhibition of antiquities.

Ironically, that same day the BBC's Vietnamese Service posted an interview with historian Duong Trung Quoc, one of the few non-Communist members of the national legislature, on the significance of the land reform exhibit. Dr. Quoc was upbeat.

"We need to discuss our mistakes, our failures… Sixty years have gone by. If we cling to the notion that all the landlords were evil people who exploited the peasants, while the peasants were all fine people… then our society won't learn lessons from the past and our young people will just be turned off."

David Brown is a former US diplomat with detailed knowledge of Vietnam