Dorian Lynskey is a prominent music critic and has written a thoroughly researched history of 20th century protest music. In his book, 33 Revolutions per Minute: A History of Protest Songs he explains how protest songs force their way into a culture and everyday conversation.
Some of the artists he explores are Billie Holiday, Green Day, Woody Guthrie, Bob Dylan, Nina Simone, James Brown, Stevie Wonder, the Clash, the Dead Kennedys, Public Enemy and Rage Against the Machine.
He investigates their songs from a social context, like civil rights, the Vietnam war, black power, gay rights and the opposition to the wars in Iraq.
33 Revolutions is an excellent book and is well recommended as a way to fully understand the protest song.
My covers and original protest songs are together in one album called The Protest Project and it’s available for free at kregmusic.com