The "anti-Vietnam War" movement, despite its pacifist-sounding name, employed doublespeak and other deceptions to argue that the U.S. (and only the U.S.) should get out of the war and "let the remaining parties fight it out themselves". An example of the deception is the slogan, "War is not healthy for children and other living things," implying that if only the US would stop supporting South Vietnamese independence against Soviet-supported North Vietnamese aggression, there would be no more battles, no more civilian casualties or homeless refugees.
Actually, the U.S. did withdraw in 1973, which led to an immediate ten-fold increase in civilian deaths: over 500,000 people died in internal purges (i.e., they were murdered by the new Communist government put in place by the North Vietnamese conquerors) which was justified by American "anti-Vietnam War" activist with the slogan, "You can't make an omelet without breaking eggs." This of course, in horrifying irony, contradicts their other slogan about war not being healthy.
Meaning of "anti-war"
For a more detailed treatment, see Anti-war.
A deliberate and well-orchestrated campaign of disinformation was put into place in America, with collusion from liberal journalists like Walter Cronkite.