Various commentators have mentioned that the ethos of the 18th and 19th Centuries disapproved of sharpshooters, who were seen as acting in a cowardly manner. Some even considered it unchivalrous to take aim at an individual foeman. Here’s an example in an editorial that appeared in the Missouri Democrat in December, 1862.
Major-General Hindman, it appears, had been issuing lately another of his characteristic orders or addresses to his troops, telling them how to shoot, and whom they must shoot. You have published already one of Hindman’s “orders,” upon the subject of “picking off pickets,” killing off “pilots on steamboats” etc. That was an atrocious document; but his “Address to the Troops,” issued on December fourth, only three days before the late battle of Prairie Grove, when he was crossing the mountains to attack us, I think it excels it in infamy! Who ever before heard of the commander of an army, among civilized nations, instructing his men, in a public address, to single out mounted officers in the ranks of his foe, and deliberately shoot them down? Oh ! shame upon such chivalry; yet this is the conduct of which Hindman has proven himself capable.