Unfortunately, many people who go to see the movie will probably accept every little detail as fact.
(I have to admit, I myself knew and still know very little about the Crusades. Until recently, I had been taught that it was a war started by Christians to force Christianity on other parts of the world).
I think most of the people who go see it will see it for exactly what it is: a fictional movie, entertainment, and a lot of over saturated orange scenes (Scott likes to do that, orange or blue, glare or hyper-shadow). Most folks go to movies for fun, not for education. And I think it's hilarious the primary critic here is a guy speaking a year and a half ago, primary photography wasn't even done forget any editing.