Are not the Robin Hood ballads about a bunch of renegade communists re-distributing wealth from the capitalist of yester-year back to the working class? A lot of songs about poachers have the same sort of message.

Jacobite songs? There are many songs writen with wars or battles as a subject - these aren't political? "Hard Times of Old England?" (I don't know how old that is.) It wasn't always easy to criticize one's own government, and the songs probably had to be disguised so anyone who either didn't understand, or didn't want to understand would miss the political message. So basically, if you don't want to see it, it's not there.