My favorite writer on race and class in the USA, Adolph Reed Jr., has written about Django Unchained and a few other movies in Django Unchained, or, The Help: How “Cultural Politics” Is Worse Than No Politics at All, and Why. I wish I had time for a proper response, because I think Reed is right to quibble with Django Unchained, but he misses its strengths. Evan Spiller offers a solid response in Neoliberalism Unchained?
If you don't have time for Reed's now, the funniest thing in it is a reference to Tarantino as "the Chance the Gardener of American filmmakers", which misses Tarantino's virtues but nails his weaknesses. Spiller's is short, so you can read it without Reed's—and if the issues interest you as much as they interest me, that'll make you read Reed's. Brilliant people are fascinating, especially when they're wrong.