The death of Peyton Farquhar

What was the advantage, for the Union, in deceiving, tricking, and killing Peyton Farquhar? It is explained in the text that Farquhar is "a well-to-do planter, of an old and highly respected Alabama family" and he is not in the army. He was, however, "naturally an original secessionist and ardently devoted to the Southern cause," and "he did what he could" to support his side. "No service was too humble for him to perform in aid of the South," the first paragraph of part 2 reads, "no adventure too perilous for him to undertake if consistent with the character of a civilian who was at heart a soldier." Anyhow, there would have been a lot of civilians in the South who would have felt the same way. Was it the fact that he was wealthy, which would have made significance to the people, including both the Federals and the Confederates? Being rich, would mean that the person or the family own slaves, which is definitely true for Peyton Farquhar who is "a slave owner." The Federals, who, at least appear to, believe, strongly in the immorality of slavery, would have loathed the wealthy slave-owners, and therefore, they slaughter the man. This may not be a "smart move" since the man's slaughter would not give the Federals victory nor would it end slavery. Also, there would have been a lot of other wealthy Southerners who would have had the belief. Why Farquhar? Could it have been any Southern civilian? Was it to show an example to the other Confederates so that they would not do the same thing, as a warning from the Union? Is this insignificant and we, as readers, are not supposed to care or is the short story trying to convey something by indicating a death of one civilian and not focusing on army combats and soldier deaths?