In "Just Lather, That's All," the narrator's primary role is that of a barber, and it is clear that he really enjoys it. He mentions that he performs his work "honourably," and describes himself as being "conscientious" and the "best" barber in the town.
Aside from his work as a barber, the narrator is also a rebel spy who has tasked himself with the job of murdering his enemy, Captain Torres. The narrator has chosen this path for two reasons: firstly, because the Captain has murdered many of his friends and fellow rebels and, secondly, because he cannot simply let him walk out of his shop:
So it was going to be very difficult to explain that I had him right in my hands and let him go peacefully—alive and shaved.
The narrator soon realizes he cannot murder the Captain because, deep down, he is fundamentally opposed to the concept of taking somebody else's life:
No one deserves to have someone else make the sacrifice of becoming a murderer. What do you gain by it? Nothing.
So, while the narrator enjoys being a barber and a spy, he is very uncomfortable with the idea of being a murderer.