A brutal, but very good movie with a strong anti-racism message. Edward Norton (as usual) was phenomenal. I commend you for wanting to have a positive influence on your friends. If you do get your friends to watch it with you, I encourage you to use it as a platform for discussion afterwards. Ask them what they thought the central message of the movie was and what they think of the message. Oftentimes discussing something helps to reveal one's own prejudices and/or biases. Self-revelation/awareness is one of the most powerful tools for change. Hopefully they'll begin to see the need for change in themselves and can then act upon the conviction.
Good luck to you in your endeavor.