It got the "let little timmy play too" vibe all over it. It hints that there are no interesting historical events with black people having a major role in it that you would want to create a movie about.
Option A: Take a story with a white cowboy, cast a black guy for him and shoot the movie.
Option B: Find a story of a black cowboy (and as you said there were many of them) and shoot a movie about it.
IMHO option A is patronizing while option B is empowering. Because option A assumes there were no black cowboys, there are no good stories too tell about black people.
And this is the right way to do things, and not by pity race swapping some famous character/historical figure.
Let me try to elaborate on my argument. Imagine you are in a park and there are three children playing, child A, B and C. Imagine child A has 10 toys, B has 7 and C 1.
Now if you forcefully took toys from A and B and gave them to C, then that's patronizing behavior as it means "you can't have your own toys, you need to steal them from someone else, you are not good enough".
A more respectful way of solving the dilemma for all involved parties is by just getting more toys for child C.
Also, this does not particularly look like Brad Pitt. If you are referring to the greyish color of the marble, be aware statues were painted in antiquity.