I just think seeing parallels between the Vietnamese Communist-led national liberation struggle and the recent Taliban takeover, even in matters of postwar retribution, is wrong. I see how it's tempting, despite the historical specificities, and given its the latest example of the awesome military power of the United States leaving behind another failed venture.
After thwarting possibilities of a peaceful democratic process of unification and deliberately escalating a situation towards military intervention, a favoured government was installed and hastily built up by violence which then began to quickly crumble when the Communists restarted armed struggle. That struggle in the southern Vietnamese countryside from as early as the 1950s was brutal and pitiless, and we're talking about a severed heads and other body parts left as clear messages to political enemies level of brutality here. The informants at the lowest level were hamlet-dwelling peasants, and the motivations or pressures for them doing so are more complex than just dobbing in the local reds, but hunting down those who were part of disappearing other ordinary people, who were then tortured, raped and shot isn't the same as Talibs kicking in the doors of journalists, teachers, even just drivers for occupation personnel, or taking their family members as second prizes.