I think you writers are often too much like English teachers, you over analyze everything. I read the story and I thoroughly enjoyed the story. Whether Mason should have killed the rapist to start with or not is immaterial, no one knows how others will react to a situation. Most people don't really know how they will react until given situation occurs. I think that Cole has done an excellent job in portraying Mason and the thought process that he went through. It just gives the reader a better insight into the character of Mason.
I will never forget a freshmen English class where we were a assigned a story to read and then discussed it in class. When the professor gave his interpretation of the story, the only thing that I thought was "You have got to be shitting me". I think most stories are written for the pleasure of both the writer and the reader and rarely contain some deep hidden meaning.
I always enjoy reading Cole's stories and this was no exception. It was very well done. I have no doubt that of all the characters in the story that Mason and his integrity were head and shoulders over all of the rest.