Interesting. But I'm not sure we actually got much of a character growth arc out of either Django or Schultz. Schultz didn't like slavery from jump, though he was not above using it to get what he wanted from Django. And Django wanted his wife back from jump and never wavered in that.
Perhaps Django's attitude toward other slaves changed, but I would argue that he was merely playing a role at Candyland until he and Schultz got exposed. So it wasn't like there was a sea change there either. More that he had to bury his real feelings until he accomplished his objective.
With Schultz, feeling some responsibility for Django, as well as disgust over slavery, it felt like a logical progression for him to take action against Candie like that. I don't think it was an epiphany kind of moment. Even his action, which imperiled Django and Broomhilda, didn't seem like a change in his character to me.