you have some bad misconceptions of this movie. It is full of clever and hilarious humor aimed in every direction (meaning to and from the black and white characters about both the slaves and slave owners.) It also does a great job of developing the the character of django as he goes from slavery to free black man and has to 'act like he belongs' as every black person he is around is still a slave.
I strongly urge you to reconsider seeing this movie as it is honestly one of the very best movies I have ever seen and I think has the possibility of becoming an all time great.
without giving too much away killing white people is not djangos main motivation, merely a small perk considering his plight and at some points shows that he has a second thoughts about taking life.