I dont remember Howlin Wolf, John Lee Hooker, Robert Johnson, Jerry Lee Lewis, Elvis Presly, Johnny Cash etc. protesting about anything.
Apparently youve never heard Johnny Cashs
"The Ballad of Ira Hayes," which touched on injustices against Native Americans. Or John Lee Hookers
"I Dont Wanna Go To Vietnam" ("We got so much trouble at home, we don't need to go to Vietnam").
From a Living Blues magazine article:
"Southern Exposure was the third album by Josh White, a young singer who was then staking out a unique position in American music: he was the only musician ever to make a name for himself singing political blues. Oddly, he made no claim to uniqueness; like Wright, he argued that the blues was by its nature a protest music, and decades of writers on the subject would concur."
However I was mistaken to include rock n' roll. While there might have been a few songs dealing with societal issues (Chuck Berrys "Too Much Monkey Business" being one), they mostly began appearing during Lennons career.