The Tet offensive changed the anti-war situation profoundly. Before Tet, overt opposition to the war was marginal, the province of radicals, religious fanatics, hippies, and other elements not taken very seriously by the ruling class or the public. After Tet, major politicos began to slither over to the anti-war side. Also, different people came to be more prominent as anti-war leaders. In 1965, opposition to the war was coming from groups like Women Strikle For Peace, the Society of Friends (Quakers), and small campus-based groups, who emphasized discussion and education. After Tet, new organizations appeared, led by people like David Horowitz and Jerry Rubin, who had much different methods, one of which was to put a lot of people in the streets and thus affect the mainstream debate on the war which had now begun. I think many of the new leaders may also have had delusions of being part of a new, revolutionary leadership which was going to take power somehow. One becomes like one's enemy. However, what else were they going to do? The pre-Tet organizing was geared to people who think and question the order of things; most people just go along with what's happening. If the primary goal was to stop the War in Vietnam as soon as possible, the methods of the post-Tet organizers would seem to make the most sense. Maybe they weren't very effective, but what would have been? In the short run, handing out leaflets and running teach-ins explaining why the war was bad didn't affect policy at all -- one doubts that outside of the FBI, the government was even aware of it.
-- Gordon