The Blue Tail Fly is a song about how the slave is happy his master's been killed. Half the rest are about the problems of the average worker and poor farmer trying to make a living. A sympathy with those folk and those conditions often has a reflection in political stances, generally left of center. But not, of course, exclusively.

Now this is too simple an answer, you are looking for something more subtle, right?

Cheers, Larry C.