I have both Tennessee Ernie Ford's "Civil War Songs of the South" which has I Can Whip the Scoundrel and Hermes Nye's "Civil War Ballads" related recording, General Patterson, and neither singer offers any concrete insight into who Abner is.

The folks at Fresno State were unable to ascertain with any certainty who Abner was (link). Though Hermes Nye includes verses about Abner in General Patterson, that doesn't *appear* to be a standard part of the song (Fresno link for that song as well.

Another name I've heard suggested is Gen. Abner Doubleday, a Union leader at the Battle of Gettysburg. A long-standing myth is that the battle was fought over a shipment of shoes, a supply which both armies needed, however, that doesn't sit well with me for a few reasons, namely that that explanation fails to get at the meaning of Baldwin in that case.

The Abner Perrin argument is enticing since his name is Abner and he died while trying to re-take the Mule Shoe salient, but to me that still doesn't explain Baldwin.

I have to second "Reb's" opinion that the most likely Abner was Col. Abner H. McCormick of the CSA. I have found the following passage:

"Brigadier General George H. Gordon, USA, commanding District of Florida, commanding Union expedition on the St. Johns River, reconnoitered the vicinity of Palatka, reported no Confederates at Camp Finegan, and Southern forces in East Florida were: "At Camp Milton, the Second Florida Cavalry, Colonel Abner H. McCormick, CSA, 600 men; Camp Milton and McGirt's Creek strongly fortified. At Baldwin, no troops, strong fortifications, two pieces of artillery." (Source, PDF page 346)

Haven't found anything specifically tying Abner McCormick to shoes, but to me that to me makes the most sense.