Friends wanted to see Django Unchained, so I saw it a second time. I think I liked it more this time, because I knew the conclusion was going to be nothing but spectacle. Tarrantino's a master of genre artistry: he creates worlds that are true to themselves, dreams or nightmares where humans behave by the logic of their genre—in this case, the spaghetti western—rather than the real world.
A quick breakdown of the historical inaccuracies in Django Unchained, focusing on slavery:
In the film's opening shot, it looks like whipping is standard treatment for slaves. It wasn't. The threat of whipping, like the threat of being separated from their family, was most effective when that was the exception rather than the rule. A scarred slave was a damaged slave, and a scarred slave usually inspired buyers to ask why the slave was whipped. No one wanted to pay top dollar for a slave that was insane or some sort of troublemaker. (In Henry Watson's account of being sold, he says, "If they discover any scars, they will not buy; saying that the nigger is a bad one."
Django's owner gave orders to sell him cheap. That would be like a horse trader saying to sell a horse cheap: it's a good line, but bad business practice.
Candie says slaves are property, and he can do anything he wants to his property. Not quite true: there were some laws to protect slaves. But as noted in Slavery in the United States | Economic History Services: "prosecuting masters was extremely difficult, because often the only witnesses were slaves or wives, neither of whom could testify against male heads of household."
Slaves and free blacks rode horses, and about 10% of the US's black population in the 1850s was free, so all the goggling at Django is purely for dramatic purposes.
"Mandingo fighting" was pure fantasy—Tarrantino got the idea from Mandingo, a 1970s exploitation flick. A healthy male slave was too expensive to use so casually.
But despite the many inaccuracies, the greater truth remains: slavery was an abomination. Quibbling about the details in Django Unchained is like quibbling about the details in a Robin Hood story: that misses the point.
Recommended: How Accurate is Django Unchained? On Riding Horses, Mandingo Fighting and Dogs Eating Slaves
Bonus: The trailer for Mandingo: