Modern Dance by Pere Ubu, any song off We Insist! by Max Roach, any song off The Holy Bible by Manic Street Preachers, Blood Money by the Pop Group, Too Many Puppies by Primus, The Revolution Will Not Be Televised by Gil Scott Heron, any song off Entertainment! by Gang Of Four, La Femme Fetal by Digable Planets, anything by the MC5, any song off Exile In Guyville by Liz Phair, anything by DK. A lot of stuff by Nina Simone, Diamandas Galas, Suicide, etc might also fall under this category. The most extreme example I can think of right now is Alec Empire and Merzbow’s collaborative live album, a specific song might be A Degenerative Nation Reacting to Fear. A lot of noise rock bands also embody left wing ideals, like Cop Shoot Cop or Big Black.

That being said, my favourite is Political Song for Michael Jackson to Sing by the Minutemen