When I say "humanize" I mean it in the sense that the scene pretty much made people forget just how evil those men actually were. Obviously QT used them as objects of humor and portrayed them as complete buffoons. My point is that in doing that he made light of how evil/despicable/dangerous those men actually were. That scene almost made them seem harmless, that's why it's so funny. That scene was so over the top and cartoonish that you couldn't even take it or the kkk like characters seriously, and that was the point.
First off it wasn't the KKK, which was not founded at the time. They were a rag tag group of racists out trying to kill a black man and his white friend; pretty evil thing to do, in the eyes of MOST people who saw the movie.
QT films always portray moments of levity in dangerous characters. Consider the ridiculous conversations two hit men continually got into in Pulp Fiction, or how comical yet dangerous the Jew Hunter was in Inglorious Basterds. Yet in Django, these characters are not portrayed in a positive or effective light - they're objects of scorn, ridicule, and disgust. The rest of the film features very serious racists who are very good at being racists (Candie especially), so the notion that the film trivializes slavery is just stupid. I don't think it's a stretch to suggest most non-rich slave owning southerners in 1858 were dumbasses.
No one left that movie thinking "oh boy, why were blacks so afraid of slavers back then, they were clowns lolll." Nah b. I thought it was brilliant the way QT flipped stereotypes throughout the film. Hell, nearly every white character in the film is a dumbass. Even the formidable Candie clearly wouldn't be as dangerous without the true brains behind him: Stephen, the black slave.
People are just looking for something to be offended by. When was the last time a major blockbuster film featured a black protagonist killing evil white people? When was the last film that portrayed slaves getting whipped, branded, castrated...and all the other stuff that history books leave out? And yall are complaining? If a black man directed this you'd be jumping for joy