How does the writer use conflict to advance his message in “The Short Happy Life of Francis Macomber”?

In this famous short story Hemingway presents a triangle of two men and a woman, in which the conflicts among the participants are as crucial as their romantic or sexual attraction for one another.
It is something of a mistake to regard this as a love triangle between Margot, Macomber, and Wilson. Margot and Macomber, though still married and, for financial and face-saving reasons, not planning on divorce, have no love for each other any longer. Wilson, though he gladly takes advantage of Margot's nocturnal appearance in his tent, doesn't love her—he hardly knows her—and primarily feels contempt for her. Wilson also correctly views Macomber, until the latter's transformation in the second half of the story, as a coward and a "bloody four-letter man" who is concerned chiefly about his public image. Macomber, of course, hates Wilson. He already envies Wilson for his cool bearing in the face of danger, but after Margot admits she's slept with Wilson, Macomber hates him more than "any of the many men he had hated in his life."
All of this conflict creates the situations that drive the plot forward, and the plot is the means by which Hemingway expresses his basic theme: that fear of death is irrational and self-defeating. Wilson quotes lines to this effect from Shakespeare's Henry IV, Part 2: "By my troth, I care not. A man can die but once. We owe God a death." Macomber himself does not realize this or accept this credo until his wife has made a fool of him. And Wilson probably would not have taken advantage of Margot's visit to him had he not felt such contempt for Macomber after Macomber's display of cowardice in running from the lion.
Hemingway's theme is also one of male bonding. It's difficult not to see sexism and even misogyny in his attitude. But it can also be argued that the solidarity and courage of men is more at the center of Hemingway's approach than negativity about women. When Macomber flees before the lion, we are told, "two black men and a white man looked at him in contempt." Hemingway thus sees male bonding crossing racial lines, perhaps in this moment obliterating racism as a divider. At the close of the story, the catastrophe is precipitated by all of the conflicts coming together: Macomber's attempt to prove himself in the face of Margot's and Wilson's (previous) contempt is successful, in spite of his death; and Margot's hatred of her husband causes her to shoot him. The death of Macomber is the final illustration of Hemingway's theme: a man has given his life and proved his worth at the highest cost possible.