Just as food for thought, and not necessarily because I disapprove of the casting of Heimdall on its face (the Warriors Three, after all, seem to be modeled after an Englishman, a Scot and a Mongol) - and definitely not because I recognize Sif's Jaime Alexander as Jesse from the show Kyle XY - but isn't Nordic culture also something worthy of treatment and exploration? While still technically European, Scandinavia's kind of up there by themselves compared to England, France, Italy, Germany, countries that form the core of the European experience. The producers must have thought so a little bit, since they cast Stellan Skarsgard in the film, but they took advantage of the opportunity to go diverse (again, prompted in no small part by the already-diverse collection of Asgardians) rather than go full-on Nordic and highlight anything particularly unique about their culture.
My problem with political correctness is not in getting terms like n***er and wop and kike out of the American lexicon, my problem is when people file lawsuits when asked to turn off their cell phones in a movie theater [http://jonathanturley.org/2011/02/23/delaware-supreme-court-overturns-ruling-that-movie-announcement-to-turn-off-cellphones-was-racist/]. The version of Political Correctness that is most universally supported is also known as Just Being Polite and Sensitive to the Needs and Wishes of Others, which people should be doing anyway without a racial or similar component. That makes a lot more sense to me than to say that if I'm not treated fairly for whatever reason, I should just suck it up because some other white guys did the slavery and colonialism bit a hundred years before any of my ancestors got on a boat from Germany (they missed both slavery and the Third Reich by a good 30 or 40 years each, and never lived anywhere but Ohio thereafter).
There actually seems if anything to be a triple-standard in Hollywood - not just double - whereby "Negroid" culture should be preserved and well-represented at all costs, any "Caucasoid" culture regardless of distinction from any other (e.g. Nordic vs. Italian) is expendable for purposes of diversification, and "Mongoloid" cultures are subject to "whitewashing" in order to mainstream an Eastern story for a Western audience. That last aspect is especially ironic as Asian characters are sometimes tossed into the "token diversity" mix, meaning we have Asian characters to keep a movie from looking "too white" and white characters to keep a movie from looking "too Asian" (see also: Airbender).
The real shame of this is some of the most memorable characters in cinema are simple, honest representations of their culture. Pat Morita, while American-born, is strongly descended from Japanese and portrayed a number of Asian characters in TV and movies (a Japanese navy admiral, a South Korean army captain, the emperor of China). The particular example I'm thinking of is the immortal Mr. Miyagi, where aside from training Daniel-san, he also gave a stirring insight into the inhabitants of Okinawa, occupied by US forces in WWII (our bases still take up about 20% of the island), and many of whom signed up to fight with the Americans to prove their loyalty, even as their families were interned (Miyagi lost his wife and son in Manzanar). He was the personification of a noble people in the face of wartime policies whose morality and effectiveness were questionable.
So I don't know if casting Heimdall black deprived America of a good glimpse into Nordic culture (considering it's a superhero movie based on their ancient mythologies, the impact is probably minimal), but it was a damn good casting. Casting a white Miyagi definitely would have deprived people of a glimpse of a tiny Pacific island culture, and while Airbender may yet be just another fantasy film, I think as a whole, culturally-accurate casting can have the real impact of introducing people to new and unique cultures, and not the feel-good faux impact of having every story sprinkled with one of everything. Another good example would be Invictus, which explored not only the rampant racial tension that continued long after the end of Aparthied, but also Mandela's efforts to build bridges for reconciliation more than restitution.
