Leeneia, I would posit the idea that the ballads are not necessarily about the immorality of the upper classes, but about the way people in general can treat each other. They make us question who we are as human beings and how we should treat one another, what we expect from relationships with other people. Pretty much every single Child Ballad has a relationship between two characters which is then threatened by a third character as the central problem of the story. If you want to read a really good study about the way the ballads functioned in rural 18th century Scotland, I highly recommend David Buchan's book The Ballad and the Folk.