Honor really was that important to men in the eighteenth and nineteenth centuries, particularly Southern white men, and any actual or perceived loss of honor did have social/political/economic ramifications. Bertram Wyatt-Brown, the preeminent historian on Southern honor, concluded that honor played a significant role in Southerners’ lives, but it was especially important to elite white males. The same was true for modern Europeans and Spaniards in colonial Latin America – a double moral standard existed, differentiating honor between the sexes. Race was also a factor in considering honor and historians such as Wyatt-Brown and Kenneth S. Greenberg assert all people had honor, including enslaved blacks and Native Americans; the difference between them and elite white males was in the way they demonstrated and defended their honor. In the nineteenth century, honor was more than a vague concept meant to instill morals. It was an integral part of a person’s private and public identities. Internalizing honor to such an extreme made men exceptionally sensitive to any sort of criticism or insult, which explains part of the high level of violence in the Old South.

More than just a code of ethics, honor dictated personal and public relationships and established social norms. Antebellum Southerners, like members living in honor-societies in the Mediterranean and colonial Latin America, saw their reputation as the only source of their self-worth and their social standing in the community. According to Bertram Wyatt-Brown, “the concept of honor was designed to give structure to life and meaning to valor, hierarchy, and family protection.” In the Old South, insults could not be tolerated because they had the potential to disrupt power relations between men and women, elites and the lower-class, and most importantly, whites and blacks. Honor was a fragile and vulnerable thing; open to constant attack from those who would tarnish an opponent’s honor in order to elevate their own social standing.

Its importance for Southerners declined after the Civil War, when dueling all but vanished. Southern elites began using different traits to measure their "worth" as gentlemen, usually by focusing on business and political ventures like Northern men had been doing for decades. It's not to say that honor and its defense completely disappeared, but Southerners no longer emphasized martial valor like they did in the antebellum years and putting their lives on the line for an abstract concept did not have the same glory that it did before the 1860s.

Some sources: Bertram Wyatt-Brown, Southern Honor: Ethics and Behavior in the Old South (New York: Oxford University, 1982). Bertram Wyatt-Brown, Honor and Violence in the Old South (New York: Oxford University Press, 1986). Bertram Wyatt-Brown, The Shaping of Southern Culture: Honor, Grace, and War, 1760s-1880s (Chapel Hill: University of North Carolina Press, 2001). Kenneth S. Greenberg, Honor and Slavery (Princeton: Princeton University Press, 1996). Robert A. Nye, Masculinity and Male Codes of Honor in Modern France (Berkley: University of California Press, 1993, 1998). Ramon A. Gutierrez, When Jesus Came, the Corn Mothers Went Away: Marriage, Sexuality, and Power in New Mexico, 1500-1846 (Stanford: Stanford University Press, 1991). Lyman L. Johnson and Sonya Lipsett-Rivera, eds., The Faces of Honor: Sex, Shame, and Violence in Colonial Latin America (Albuquerque: University of New Mexico Press, 1998). Pieter Spierenburg, ed., Men and Violence: Gender, Honor, and Rituals, in Modern Europe and America (Columbus: Ohio State University Press, 1998). Craig Thompson Friend and Lorri Glover, eds., Southern Manhood: Perspectives on Masculinity in the Old South (Athens: University of Georgia Press, 2004). Timothy R. Buckner and Peter Caster, eds., Fathers, Preachers, Rebels, Men: Black Masculinity in U.S. History and Literature, 1820-1945 (Columbus: Ohio State University Press, 2011).

You specify when, but not where?