While we have seen anti-war demonstrations about the Iraq War, these pale in comparison to the Vietnam War anti-war demonstrations. Now, forty years later, it's easy to forget just how strong the anti-war sentiment was, and how hated the soldiers were by a huge number of Americans.
While we see some anti-war demonstrations, marches, etc., now, back then the anti-war action was almost continuous. You can see a nice timeline of the anti-war actions on Wikipedia.
Where we have anti-war marches and speeches now, in the 60s and 70s we had massively huge marches. Students took over universities. There were riots and draft-card burnings. Buildings got burned. There were sit-ins and self immolations. Eventually we even ended up with soldiers killing students at Kent State.
Anti-war and anti-soldier sentiment was rampant. News like the My Lai Massacre reinforced the public's view that the war was evil. There are trials today for inappropriate actions by military personnel. Civilians get killed. It's nothing like the horror that was My Lai.
The nightly news reinforced the horrors of Vietnam. From a strictly selfish viewpoint, they'd announce the weekly death count of American soldiers in Vietnam. In 1968, more than 16,000 American soldiers died. In 1967-1969, it was almost 40,000 soldiers.
And the soldiers were hated. They were all called "babykillers" and monsters. Many of the soldiers in Vietnam had been drafted into military service. They weren't there willingly. It didn't matter. If you'd worn a military uniform, you were a monster.
This was the atmosphere that Hayduke came back to.
Here are some books that can help you remember the atmosphere at that time:
The War Behind Me