Philadelphia – Near the end of the hit movie Avatar, the villain snarls at the hero: “How does it feel to betray your own race?” Both men are white – although the hero inhabits a blue-skinned, 2.75 metre-tall, long-tailed alien. Strange as it may seem for a film that pits greedy, immoral humans against noble denizens of a faraway moon, Avatar is being criticised by a small, but vocal group...