Although I am not a movie critic, nor can I assume I understand what messages the director and writers wanted to impart in the movie Sling Blade, I believe that Harry Kiely ("The False Promises of Violence," November-December 1997) missed the essential point. Kiely indicated that this movie is based upon the premise of "redemptive violence" and that it exhibits a flawed presentation of good vs. evil traced to Babylonian creation myths. This may be a simplistic view of the movie and ignores what I feel is the more important message.
Karl represents a simplistic, judgmental evaluator of good vs. evil and acts accordingly. At the risk of insulting developmentally disabled individuals, the use of Karl in this capacity has been selected so that we can see that non-critical, non-thinking judgment of others can easily result in tragic conclusions, such as the brutal killing of Doyle. Doyle was not portrayed without some level of sympathy in the movie, as witnessed by his acquiescence to his own death.
I did not take away from the movie any feeling that Karl was justified in his actions, just that he was playing out a judgmental script that was ingrained in him. The movie is a request that we must never just react in judgment of others. Good vs. evil is rarely a black-and-white event.