Not an ex-hippie, always a Republican, but the film is about two guys, the open road, and the money they have stored in Captain America's fuel tank. This was supposed to have them on "Easy Street", so they hit the road to see America. The only problem is that the 60's era "counter-culture" which was so openly embraced by those on the Left coast and the Right coast, wasn't so embraced in "middle America" where they met with their demise.
They sampled all that was going on at the time: LSD trip in New Orleans with a famous future MTV star, some group love at a commune, some dope smoking with Jack Nicholson while they discuss life on other planets. Until they hit a place where their type of "freedom" is neither embraced, or understood.
So, they meet their demise, and all that cash in Captain America's fuel tank goes up in smoke, just like their dreams.
Peter Fonda says it best: "We blew it, we blew it man."
They had tried not to be what they hated: "the establishment", but wound up selling cocaine for the money that would set them free. Just like what "the establishment" does.
They became what violated them.
It's about a 5 on my scale of one to ten. Jack Nicholson stole the film. His best line: "I got enough problem with the booze, I don't wanna get hooked on that stuff".