John Moulden:

"The point I would make, as my last word, was provided by Bert Lloyd, of flawed and immortal memory: 'Folk songs do not tell us what happened; they tell what people believed happened' - however, Bert did not say as I think obvious: It is what people believe that tempers their actions. As such Folk History is intensely important in establishing some elements of 'Why?' events unfolded, as distinct from 'What' 'actually' happened."

Well what actually happened is absolutely crucial. Folk songs may provide evidence of motivation, but they do not provide justification (for instance of murder).