The Clash were innovative, radical and helped drive a change in music that was ground-breaking. In comparison to some of the music today they sounded like they meant it. I still listen to their music today to remind myself what music made with commitment sounds like.
Realism is always subjective in film. There's no such thing as cinema verite. The only true cinema verite would be what Andy Warhol did with his film about the Empire State Building - eight hours or so from one angle, and even then it's not really cinema verite, because you aren't actually there.