For me, politics and folk music are inextricably linked and have been since I first heard Woody Guthrie, the Almanac Singers, Pete Seeger, etc. as a small child.
Folk music provided the soundtrack as we marched for disarmament, for civil rights and to stop an unjust war in Vietnam. Folk music continues to supply the soundtrack for many righteous causes, including enviornmentalism. The Clearwater Festival is a manifestation of that.
At the Clearwater Festival, I've also heard a lot of great non-political traditional music.