There is one key error that RUINS the film. Yes, completely RUINS it.

This is the error of combining historical fiction with actual historical events.

Parker took an actual event--the murders of the Civil Rights workers--and then added a wholesale work of fiction onto the end of it. He should have chosen between making a purely fictional story about the era or he should have stuck to the facts of the case. Instead he made this abortion which insults the viewer at every turn. Why couldn't he have just stuck to the true story? What about the true story was not compelling enough for this idiot? In case you think I am going out on a limb here, I quote Time Magazine's Jack E. White, Jr, a black man, who referred to the film as a "cinematic lynching of the truth." I have nothing else to add to Mr. White's sentiments.