There was some great footage in "Gimme Shelter" of the hippies, and the bikers too. It was a complete culture clash. The Stones thought they were just hiring security for a free concert. The free concert in London went off without a hitch, why not the US? They were wrong. They found out the hard way that people in the US were nowhere near as civilized as they were in London (back then anyway).
I noticed that the film has some of the best footage I have ever seen of people tripping very hard, taking their clothes off, etc. I wonder what ever happened to most of these people, like the naked fat girl who kept trying to get on stage? There were a few children in attendance there too, I don't think CPS had near the power back then, that they have now.