William Wallace was hardly “knighted” by the English monarch thus would not have been knwon as “sir” anything. The lairds of the highlands didn’t need such nonsense. They knew who the leaders were. FREEDOM!!!
There’s one in every crowd. After the Battle of Sterling Bridge in 1297 Wallace was knighted by an unnamed Earl and became Sir William Wallace “Guardian of the kingdom of Scotland and leader of its army”.
But that is so tangential it is ridiculous. The obvious point was to compare the emotion one might feel after watching a rousing speech to the emotion resulting from a scene in a movie – not the applicability of the word “Sir”. Good Lord.