In "Just Lather, That's All," what makes the barber think that the Captain "is a calm man" compared to his own state of mind?
It is vital to understand the role that narration plays in this excellent short story. This story is told using the first person point of view, which means that we see everything from the point of view of one of the characters, in this case the barber. This gives us as priviliged spectators free understanding and comprehension of the barber's thoughts, feelings and motives. However, and crucially, we are not given access to the thoughts of Captain Torres, only what the barber can see and observe from his limited perspective.
Thus it is that the impression the barber gives us of Captain Torres being a "calm man" is based on the way that Captain Torres is peacefully reclining in the chair as the barber shaves him. The barber draws a comparison between himself and Captain Torres, imagining that he is not wondering about the prisoners and what he will do with them that afternoon, whereas the barber is unable to think clearly, faced with the magnitude of the decision that lies before him.