I read the great book Freakonomics a few years ago and found that a lot of it would be great to use in the classroom. One of the best stories in is about how the writer and civil rights activist Stetson Kennedy infiltrated the Ku Klux Klan and funneled info that he learned to the writers of the Superman radio show. They incorporated these details into the show and the result was a generation of kids growing up to see the KKK as the evil bad guys, as opposed to how many Southern whites had traditionally thought of the Klan.
I researched some more and put together this story and worksheet which is available for download here. It is a simple 1 page story that will hopefully motivate your students to think differently about how to fight against injustice.
Hope you enjoy it!