It would seem logical that in a short story that is as painstakingly structured as "Haircut" is, the best part would be the resolution. In a short story, the resolution holds a surprise ending or a twist to the plot that changes the import of the story. The resolution also imparts the moral values and confirms the theme developed throughout story.
"Haircut" is no exception to this formal rule. The resolution of "Haircut" presents two characters in a different light from that seen earlier. First, Paul goes on a hunting outing with Jim and seemingly coolly acts in a way that is disadvantageous to Jim. Second, when Doc Stair is called to the lakeside where Jim Kendall's body is reposed, he makes a surprising decision. As the town coroner, he has the ultimate authority for declaring murders accidental or homicide.
We know that both Doc and Paul Dickson are enraged by both things that Jim did to Julie (forcing his way into her home and tricking her into going to Doc's office). We know that Paul nonetheless volunteered to go with Jim hunting. We know that Doc confided to Paul that "anybody that would do a thing like that ought not to be let live." We know that "[Paul] let fire and Jim sunk back in the boat, dead." We know that Doc was worried enough about Paul's thoughts to go looking for him at the barber shop.
What surprises us is that Doc, acting as town coroner, immediately passes Jim's death off as a pure and simple accident:
Doc examined the body and said they might as well fetch it back to town. They was no use leavin' it there or callin' a jury, as it was a plain case of accidental shootin'.
This raises the questions that Lardner wants us to think about: What is the just dessert for someone like Jim who's bullying brutality is condoned by the community? What breach of ethics and morality did Jim's death prompt Doc Stair to commit? What did Paul decide to intentionally do regarding Jim's life? The resolution is thus the best part of "Haircut."