Question

Why did the war in Vietnam result in such widespread opposition?

Answer 1

The US was fighting the wrong war: The US supported a very corrupt SVientnam government, and the citizens wanted a change. It was a civil war, not of US economic importance (except for FIreston Rubber , a plantation owner). Secondly, the US was loosing many, many soldiers in this war. Thirdly, US citizens were being involuntary consripted (DRAFT) to go fight that nasty war. Fourth, the burden of the war fell on the poor (and black) citizens, as richer (and usually white) stayed in college (deferments) or other deferments or got peachy assignments in US National Guard assignments. (check George Bush's history, or DIck Cheney's history and the Vietnam service period)

In short, it was the wrong war, for the wrong reason, and the burden of dying for this fell on the disadvantaged.

Answer 2

Many Americans didn't believe that Communists taking over Vietnam was a threat to the U.S. But despite the protests, many Americans and Vietnamese lost their lives or their health fighting this war.

http://en.wikipedia.org/wiki/Opposition_to_the_U.S._involvement_in_the_Vietnam_War