"This could be a deliberate ironic twist, but if it is, it's a distasteful one for African-Americans. One legitimate complaint that marginalized people (women, people of color, Muslims, the LGBT community, etc.) have had about Hollywood in the past is that when they were portrayed, it was done in a negative way. The ditzy blonde, the Muslim terrorist, the gay predator are all familiar stereotypes from years of TV and movies. So much has been done in recent years to overcome those debasing images, but we still have to be careful. It's not that a black man can't be the sellout or the drug dealer, it's just that they shouldn't be if they're the only prominent black character in the story. Whether it's intentional or unintentional, that sends a bigoted message rippling through our society."
Writes Kareem Abdul-Jabbar in "How 'La La Land' Misleads on Race, Romance and Jazz."
Part of the problem is that there are too few black characters in Hollywood movies (not counting the movies that are specifically about black culture and history). If there's only one black character, he's going to be perceived as representing more than an individual.
And to be more than an individual is to be less than an individual.
ADDED: At Vulture, "The Six Shadiest Lines From Kareem Abdul-Jabbar’s Analysis of La La Land."