In The Last Airbender, a director of Indian descend cast blue eyed characters from a fantasy world that doesn't have any Earth races with white actors. The response?

>>Dozens of online petitions, many websites screeching racism and calling the movie bigoted, threads created in /co/ and /tv/ constantly screeching about whitewashing, and what an injustice it is.

In Thor, a black actor is cast as Heimdall, with the official title of "whitest of the gods" in Norse mythology. In the comic book the character is also white, Heimdall is never included as among the "black norsemen" and never shapeshifts to be black. The response?

>>RACIST WHITE KKK FAGGOTS! FUCKING STORMFRONT NAZI FUCKS! HE'S A GOOD ACTOR! YOU'RE JUST RACIST IF YOU CAN'T SEE THIS! NO ONE CARES ABOUT RACE! PLUS THAT OTHER ASIAN CHARACTER WAS PLAYED BY AN ASIAN WHO PREVIOUSLY PLAYED A SIMILAR ROLE, WHY AREN'T YOU RAGING ABOUT THAT ASIAN PLAYING THE ASIAN? RACISTS. RACIST WHITE SUPREMACIST BASTARDS!

Explain?