I know this has been out for a while, but I hadn't heard it before today:
I happened to be watching a July, 2012 Crosby, Stills and Nash concert on cable when Nash introduced this song in a very heartfelt way. The audience didn't seem to know how to respond to it when he started talking about it. They ecstatically responded at the end.
Protest music is powerful, even when performed by dirty old hippies.