Once again, I find myself pressed for time, so I'm putting up a post which I've expanded from a comment I left
Earlier this month, there was a nerd-kerfuffle over the casting of an actor of African descent as a "Star Wars" Imperial Stormtrooper. I believe there's a significant amount of racism in the nontroversy, but I'd apportion most of the blame to simple nerdrage over an alteration of "canon". For the "Comic Book Guy" contingent, a simple deviation from their interpretation can inflame passions that "mundanes" can't understand:
Some Star Wars fans were upset that Boyega was apparently cast to play a Stormtrooper. These fans claimed that Stormtroopers were clones of Jango Fett, and since Fett wasn’t black, no Stormtroopers should be. There is only a black Stormtrooper because of “political correctness,” they lamented.
Despite the fact that "Star Wars" is fiction, I'll play along with the canon-trolls... In the fictional milieu of the "Star Wars" saga, the original Stormtroopers are, indeed, clones of the Jango Fett character. In the course of the movies, these clones exhibit such poor marksmanship that they are the "trope namers" for bad shots. Even the "higher quality" clone, the bounty hunter Boba Fett, was an incompetent boob who was killed by a blind man and George Lucas' vagina dentata anxiety. Given the poor performance of these clones, the Empire must have made the decision to recruit competent individuals in a bid for its very survival, so the ranks of the military would eventually be filled by individuals of all races, from all planets (except for critters like this which couldn't be equipped with helmets). Of course, these new merit-based hiring practices weren't put into place in time to save the Empire.
The people complaining that there's a black Stormtrooper (of course, this assumes that the character isn't in disguise) are the same sort of people who whine about affirmative-action subverting the meritocracy when a qualified minority candidate is hired instead of the boss' golfing-buddy's "gentleman's C" earning frathole son.