I don't wish to compare, however, I think it has to be taken into account that authenticity is a major factor as yet. If you take the film Amistad, also based on a major historical event, two relatively unknowns were cast. It was a box office hit!
Eventhough it was Spielberg directing, he recognized the talents of Djimon Hounsou who came to Hollywood not knowing English. He played the lead next to Matthew McConnaugnehy also very new. They both stole the show and Mr. Hounsou learned English incredibly for his role and was astounding.
Cast among Anthony Hopkins and Morgan Freeman to further attract an audience, this with the appropriate publicity got people interested.
Danny Glover is well respected and having played along side Oprah in Beloved, no doubt she will be curious and supportive in endorsing his film. As well, as I mentioned before, with Angela Bassett who we haven't seen in a while but adore and Don Cheadles who with Hotel Rwanda and Crash to his credit will be a given to attract an audience of all sorts.
With this publicity and critics seeing the film at debuts, I thoroughly feel a thumbs up beforehand always influences the publics opinions. I respect the argument entirely.
However, if not Jimmy...just not Wesley....he could be what turns people away from the project. Thanks!