If I remember right he said 'it worked ok in Vietnam'.
The Vietcong didn't win that war. The regular North Vietnamese Army won the war. The Vietcong assisted, and were part of the strategy, but were almost entirely wiped out after Tet. I'm not saying you don't know this, I'm just retorting to what that guy said. In the end, the US and North Vietnamese government came to an agreement, where the US agreed to stop killing them, and left. Then the NVA swept down and overran the country a few months. Insurgents can typically keep fighting at a low intensity, but they haven't had the ability to win a war on their own for a very, very long time. Even in the cases where insurgencies outlast an occupation, they typically only do so, when they have third party support from another national actor.
I'd echo the sentiments of another poster who brought up the US independence war. Washington HATED, no, hated isn't strong enough, he absolutely despised the militias. He threatened to cut them down, himself in one battle, where they were blocking the post road retreating, and delaying the continental army from using the post road to advance towards the enemy. The regular army hated them too, and so did the British. They ran, or surrendered, in almost every single major military engagement of the entire war.
Following the Tet offensive, the Vietcong, were essentially wiped out. They never recovered from the losses they took at Tet, and following Tet, the Vietcong played an even more minor role in the war. The NVA had to pick up the irregular duties that the Vietcong could no longer carry out due to the collapse of their military forces, and political leadership. Tet was so disastrous for the NVA and VC, that Giap had to essentially reset the entire war. In classic guerrilla warfare, there are 3-4 stages. Stage 1, retreat to a safe base of operations to gather strength (materiel and personnel). Stage 2, carry out low intensity attacks against government military/institutions/infrastructure. Stage 3, engage government forces in a conventional military operation to defeat the government and seize control. If you fail at any stage, reset to stage 1, and start again. Tet represented stage 3, and it broke the VC, and resulted in an enormous setback for the NVA. Only the NVA, a national actor, was able to carry on and recover.