On that subject, is the legend of Robin Hood an English debasement of history?
If nothing else, an extensive revision. According to most accounts relative to the modern legend, RH would have existed a century sooner, not that much after the "Norman" ascendancy to the English throne: during the time of Richard I. Richard I was the foremost leader in the Third Crusade and had subject areas on the continent, thus his brother John took control in the homeland while Richard spent considerable time elsewhere (including being held in prison for ransom).
Accounts of Wallace could have easily been applied as the RH character, who may or may not have actually existed as a single personage or a composite: possibly, if not probably, the latter. The century sooner setting would also have put the "common" Anglo-Saxon descendants somewhat more at odds with their Norman-descended 'lords'. Counter-assimilation sometimes moves rather slowly.