The most enlightening article, in my opinion, was this, in which the writer for the New Yorker breaks down all the problems he had with the film. Namely, they were issues of race.
For instance, he writes:
“Yes, of course, there were killers in the Old West and cruel slave masters in the South—central characters in the movie—but Tarantino juices everything into gaudy pop fantasy. I enjoyed parts of “Django Unchained” very much, but I’m surprised that anyone can take it as anything more than an enormous put-on”
I found this statement to carry water when it came to the film. Tarantino admits to following the tropes of a Western, however, I'm not quite sure why, and I don't think he is either, he made the movie in the time of slavery.
In Tarantino's own words:
"one of the tropes of Westerns and telling a story like this is you have an experienced gunfighter who meets the young cowpoke who has some mission that he has to accomplish, and it's the old, experienced gunfighter who teaches him the tricks of the trade: teaches him how to draw his gun, teaches him how to kill. Whether it be Kirk Douglas teaching young William Campbell in Man Without a Star or Brian Keith teaching Steve McQueen in Nevada Smith, or actually most of Lee Van Cleef's spaghetti Westerns that aren't with Sergio Leone -- that's kind of Van Cleef's role. Now, you go to the kung fu films -- that's always the case. There's an older guy teaching the younger guy and sending him on a vengeance journey" (full interview here)
That there is proof enough to me that Tarantino's only justification for the setting the movie in the time of slavery was to have a character (Django) who wanted and deserved revenge. He described the Western, and what he tried to do, but the people he mentioned are all white, and all remain in the trope of the Western.
Like he did in Inglorious Bastards, Tarantino once again focused his attention on horrible events, and wrote his own retelling of the past. But, I ask you... watch this following clip... can you even stomach it? Does it make you feel that he is getting his rightful revenge? Does it make a difference that none of this/something like this never happened? ... what does this accomplish?
Of course, on the flip side, the movie can simply be viewed as an "ideal past" in which a slave was rescued and able to assert his own power and kill a lot of people to get his revenge, during which he gets back his wife. So.... it can just be viewed as... entertainment?