Lardner's story uses dark situational irony to illustrate, through incidents in a closed community, the theme of justice and injustice paired with the theme of masquerading evil as humor. Paul, Doc Stair and Jim Kendall illustrate justice and injustice as Paul and Doc react to Jim. Whitey, the barber and narrator, illustrates masquerading evil as humor as he tells what a good heart Jim has while describing Jim's malicious actions, taken as amusing by the people of the closed community they live in: "he was all right at heart, but just bubblin' over with mischief."
Sometimes the second theme is described as "the banality of evil" but this is incorrect. When Hannah Arendt coined the phrase to describe Adolf Eichmann's part in the Nazi Holocaust, as she covered his war crimes trial, she meant that his was not intentional evil but rather that his blunted sensibilities caused evil while he was banally being obedient and pursuing careerism: "out of a non-ideological, entirely more prosaic combination of careerism and obedience" (OpenCulture.com). Banality is a dull, ignorant thing but not a malicious, cruel thing although both truly lead to evil.
In sociology, a closed community is a social system that is, to varying degrees, shut off--closed off--from its larger environment. This describes small towns and isolated communities in which certain patterns, dominated by certain individuals, institutions or traditions, determine the social patterns and perceptions of the whole town or community, just as Jim determine the social patterns and perceptions of his town. In the world today, we are moving in many ways toward an open global community, but in the early 20th century it was common to have closed communities, isolated from progress and advancing thought ("Haircut" was published in Liberty in 1925).
The first theme depends upon Doc Stair's education and life "up in the Northern Peninsula somewhere" before coming to town. He opens up the perception of the town's social patterns. The theme depends equally on Paul, whose mental injury gives him a simplistic, literal way of perceiving. Together, they perceive Jim's injustice, especially when perpetrated against Julie. Paul takes Doc Stair's call for justice literally: "Doc told him that anybody that would do a thing like that ought not to be let live." Then, with his mind not so dull as his community thought it to be, he contrives to get alone with Jim and administer the justice called for by malicious actions and by Doc Stair's assertion.
The two themes work together because we realize that if the town hadn't been closed to the extent it was and if they had administered justice early on against Jim's injustices, then Paul may not have had to cast himself as the administrator of final justice.
Paul spoke up and said if Jim would take him he would go along. ...
I suppose he was plottin' to get Paul out in the boat and play some joke on him, .... Anyways, he said Paul could go. ... Paul hadn't never handled a gun and he was nervous. He was shakin' so hard that he couldn't control the gun. He let fire and Jim sunk back in the boat, dead.
A theme of “The Haircut” is that people can only handle so much abuse before they fight back.
The barber shares stories without really understanding what he is saying. He describes Jim as a great guy who played interesting jokes, when the rest of the town found him a bully.
Paul hadn't never handled a gun and he was nervous. He was shakin' so hard that he couldn't control the gun. He let fire and Jim sunk back in the boat, dead.
No one suspects Paul of murder. The barber describes Jim as a “good fella at heart.” In reality, Jim treated his wife and neighbors badly.