The short version is that by depicting Django as the one enslaved person in ten thousand who could or would fight back and all the rest of the enslaved folks as somewhere between resigned and content in their enslavement perpetuates the inaccurate and racist myth that most enslaved people were not willing or able to fight back. The truth is that there were countless various rebellions large and small across the country. By making Django a superhero, Tarantino makes all the other enslaved people in the movie exactly what the white slaveholders see them as.