The Purpose of a Protest Song

Do we think that the purpose of a protest song is to change somebody's mind who has a different opinion or is it to rally the like minded people around something they already believe? In a roundabout way, that causes larger change once the tribe recognizes itself and then things can happen after that. I was thinking of, do you remember a song? And I forgot new saying it, a British new wave song from the 80s called Sing If You're Glad to Be Gay. Who did that song? Oh, what's his name? Tom Robertson.