A horror movie masquerading as a rock film

After watching the new ROLLING STONES documentary, "CROSSFIRE HURRICANE" Thursday night, I watched the 1970 film "GIMME SHELTER" yesterday.
Although the former was a more comprehensive look at the band's complete history, the latter remains more compelling -- as a horror movie masquerading as a rock film.
The disastrous ALTAMONT free concert -- plagued by death, Hells Angels' intimidation and universally "bad vibes" -- taints "Gimme Shelter" like an unspoken, terminal disease.
What's truly horrific, though, is the eclipse of the 1960s ideals by the baser elements of man's nature. 
You don't just see it happening at Altamont in "Gimme Shelter." You see it happening everywhere you look.