I've learned quite a bit of history from folk songs - some of it wrong, of course - because history teaching was so bad and folk songs interesting. So excellent idea with caution. Jesse James robbed the rich but I'm sure didn't give to the poor (unlike Sam Bass, I'm told) and Mary, Queen of Scots, did have Four Marys but two were not called Carmichael and Hamilton, nor was the latter a child killer. I'm sure a book could be written of how and why the alteration occured. As was said above we can no more write off folk songs as a method of learning history than we can - in my view unfortunately - write of Shakespear. Folk songs are v good for pub quizzes: I have been known to name all the assassinated US Presidents and their assassins thanks to Bascom Lamar Lundsford.
Doc John