Anti-white theme?
Fitzgerald is the "bad guy".
It wasn't bad enough that he left Glass, but he's portrayed as an atheist (not true).
In the movie, white men (of course) killed Glass' son, whose mother was a native. But in real life, Glass didn't even have a son.
For some reason, the writer decided to invent a son and, of course, make him half native.
All of the people that help Glass along his journey are.... not white.