As far as historical accuracy, it's all pretty much bunkum and hokum. But as far as blood-boiling action, it's skookum.
It's not like helmer Mel didn't know that. He dubbed the film "historical fantasy," which pretty much says it. Lots of wrongs being perpetrated then righted, whole packs of underdogs biting back, and all to the tune of stirring bagpipes (and swirling strings and panpipes and all).
Let's have some haggis!