There are a good few songs in which ordinary folk match wits with kings (generally outwitting them, but only just); the theme was a popular one, and I don't think there's any need to look for didactic intent, or to read hidden meanings into them. It's a mistake, incidentally, to imagine that a Scottish song must have been interfered with, or imported, if it is not anti-English! That would be a rather narrow view of history and of the relationship between the peoples of the two countries. In the case of this song, I'd be interested to know where anyone might get the idea that there are "English overlords" involved. The Scottish ruling class was Scottish, not English.

If you want some propaganda that was adopted into popular tradition, consider the transportation ballads, which frequently end with such lines as

If you knew the hardships we endure, you'd never poach again.

Francis J. Child didn't spell his name with an -e, incidentally. It's a mistake a lot of people make, for some reason.