What are the men about to do on page 31 of A Gathering of Old Men, and what role does this action have in the larger context outside of Marshall Plantation?

Two old men named Mat and Chimley are out fishing when they are told about Mathu and what Candy wants them to do. After they consider the situation, they decide to help.
Mat and Chimley, two men in their seventies, are fishing on a favorite bank when a young boy rushes up to them and tells them that Clatoo says that Miss Merle has told him to tell the two older men that Miss Candy Marshall wants them "on the place" right away. She wants them to bring twelve-gauge shotguns and to have some empty number five shells and get to the quarter right away. When the two old men ask what all this is about, the boy replies that it has something to do with Mathu, as well as something to do with Beau Boutan, who is dead in Mathu's yard. 
After the boy departs, the two old friends sit where they are, and they ponder the situation, wondering what would happen to them if they were in the position of Mathu. The two men do not look at each other, for they are deep in their own thoughts of what happens to a black man who has a fight with a white man, a man he kills.
"I'm seventy-one," Chimley finally says to his friend. Then, he recalls that Mathu is the only one of them who has ever stood up to white men. In response, Mat tells his friend, "I don't have the strength to climb under the bed," meaning that he no longer wants to run and hide from the conflicts they have always had in life. Mat ponders things a while and responds,

"I have to go. This could be my last chance. Now when we are old men, we have to be brave."

The two old men have decided to gather together with others and protect Mathu by pretending that they have all shot Beau, a Cajun farmer, a white man. These old black men hope to transform themselves with this powerful act of group assertion. This powerful act of theirs is one of self-affirmation, restoring in them their manly pride. In addition, this act by the old men may encourage others outside the old plantation to find strength in unification with others of their ilk.