You state, "The embracing of a term by some individuals that others considered derogatory is certainly not unheard of, as is indicated by Confederate guerrilla Sam Hildebrand proudly embracing the term bushwhacker (I imagine a quick survey could come up with dozens of other such examples).

I think the premmier example from the Border War would be the "Border Ruffian" label, which was meant as an insult by the abolitionist propagandists (I think Greely's man may have penned it in reference to the Missourians), but is was embraced by the Missourians (with Stringfellow the ring-leader as I recall).