While protesting against the U.S. involvement in Vietnam made some sense for those who were desperately trying to avoid military service, it is not clear why they displayed Viet Cong flags at their rallies and protest marches. People who today claim they were only expressing their conscience cannot explain why they needed to display the flag of the enemy, and burn the American Flag.
The anti-war movement has been often and erroneously referred to as the "Peace" movement. This is a non-sequitar since despite their rhetoric to the contrary, they never actually called for "peace" per se, only an end to American involvement in the war. They actually did not seem to care very much about the poor Vietnamese peasant that they accused American soldiers of killing. Especially if the North Vietnamese and the VC did the killing. And when Pol Pot went on a killing spree, they uttered not a sound. When the North Vietnamese invaded Cambodia, they said not a word. When the Soviets invaded Afganistan the did not protest. Why? Ask them.
The Vietnam War lasted for over 10 years. During that period 58,202 Americans lost their lives in an attempt to preserve the sovereignty of the Republic of Vietnam. To put this number in perspective, approximately 56,000 Americans are killed every year by drunk drivers. Yet Tom Hayden and Jane Fonda do not lead violent demonstrations outside the Seagrams building.