The Communist Party used front organizations under different names (such as "the People's Coalition for Peace and Justice"), which formed the umbrella which brought together a wide variety of Leftist entities, like the unions and the National Welfare Rights Coalition and Save Our Soldiers.
At the height of things, they had a commuter service between here and Hanoi, shuttling their operatives to the enemy's capital and they could gather hundreds of thousands of pinheads to mass demonstrations, fueled by the many young people who didn't want to fight/get hurt/die in the war and their mothers or girlfriends. It seems ridiculous that anyone would not know the marches and demonstrations supported our enemies when the VC and NVA flags were featured prominently and the had chants like "Ho, ho, ho Chi Minh, the NLF is going to win"?
Hippies were a different bunch: they were into drugs, sex and dropping out and had little to do with the "antiwar" crowd.
A much smaller percentage of us went ahead and fought in Vietnam and we carried the weight of the latest front in the Cold War all by ourselves.
Weather Underground and SDS all had roots in the Communist party.