Hollywood has a problem. It's largely run by rich straight white men who, for the most part, champion the work of other straight white men. According to well publicized statistics, if you're a black, Hispanic, female or LBGT actor of director you've not been invited to the party. Getting jobs, good jobs, Oscar potential jobs, is nearly impossible.
A filmmaker who seeks to portray major events or periods in history has at least two objectives: being as faithful to the documentary record as possible, and producing a film that reaches as wide an audience as possible. While those goals aren't conflicting per se, it's easy to see how there can be tension.