Continuity mistake: At the start of the movie, Christoph Waltz shoots the horse in the head, but later the bullet hole is seen in the horse's neck.
Revealing mistake: When Django kills big John Brittle, right when he smashes his face on the floor, a cushion pops-up. Most probably hidden among the leaves to soften the fall.
Continuity mistake: When the maids introduce Brunhilda to Schultz, she is either looking at him or sideways, depending on the angle.
Revealing mistake: Before confronting Stephen, Django shoots Candie's sister. He is up high on the stairs with her on the first floor. He is far to her right. But when he shoots her, she flies straight backwards into the other room, and you can see where her dress was pulled by a rip line.
Factual error: In several closeups (especially of Leonardo DiCaprio) it is clear that some of the characters are wearing plastic contact lenses in their eyes. These were not invented until the late 1970s.
Continuity mistake: When Django shoots the snowman, the damage to it appears/disappears/increases/decreases between shots.
Visible crew/equipment: When Sheriff Bill Sharp steps out into the street you can see a hearing aid in his left ear.
Continuity mistake: During the skull monologue, Schultz's hair swaps from messy to brushed between shots.
Continuity mistake: In the scene where Stephen is shocked that Django will be staying in the big house responding with "if you ain't got no problem burning the bed the sheets", you can see Calvin place his pipe in his left hand and start to point at Stephen with his right hand, saying "that is my problem, they are mine to burn" then his pipe is magically in his right hand again. (01:30:00)
Continuity mistake: When Schulz and Django ride up to the first plantation they visit, the number of slaves milling about in the background varies with each shot.
Continuity mistake: When Stephen brings Broomhilde to Candie to discuss her price, Stephen is grabbing the left side of her neck in the wide shots, and the right side in the close-ups. This changes back and forth.
Continuity mistake: When one of the Speck Bros. lays injured on the floor, the lamp on the floor is laying right net to the hat, or several centimeters away, depending on the angle.
Continuity mistake: When Schultz and Django first camp, Schultz is seen putting on pants and suspenders. In the next shot he doesn't have the suspenders on, but we see him hiking them up as if for the first time.
Factual error: There are no Live Oaks growing in Tennessee. They can be seen in several outdoors scenes.
Continuity mistake: When Schultz pours the beers in the saloon, the first beer has very little head as he pours the second beer. When he picks up the beers to bring them to the table, there is a lot more head on both beers than there should be. (00:15:25 - 00:16:00)
Continuity mistake: When Dr. Schultz shoots Candie, in the 'reaction' shot where it zooms in on Stephen screaming, Candie's bodyguard (the one with the mustache and bowler hat) has already turned around to see what just happened. In the very next shot he now has his back to the camera and then, a second later, we see him slowly turn around again to see what just happened.
Continuity mistake: After Calvin cuts his hand and forces Broomhilda to sit down, Stephen places his hand around her neck. A shot later it’s on her back.
Continuity mistake: In the final scene where Django asks Cora to say goodbye to Miss Lara, he holds his arm with the gun outstretched, but in the next frontal shot he keeps it lowered.
Continuity mistake: After Calvin yells "where is my beautiful sister" the sun changes between shots.
Continuity mistake: Towards the end while Django is taking the horse from the cart with the slave cage, the sun changes between shots.
Answer: Django and Schultz killed some of Big Daddy's farmhands, and he wasn't going to let a freed slave kill some of his workers. Schultz knew Big Daddy would come after them for what they did. Plus Django would never let go of a chance to kill a slave owner who was trying to kill him.