All of the characters in this ballad were playing their roles according to the laws of chivalry. Lady Barnard/Arlen was lovestruck. Little Musgrave/Matty Groves would have been abandoning his manhood if he had refused the lady's offer. The page was doing his job. Lord Barnard/Arlen was defending his honor.
Of course, from most people's point of view these days, each of them was asking for trouble. Leslie Fish disposes of the three main characters in the last line of her satire:
"But who else but a brainless slut would go for Manly Men?"