I'm referring to this scene from the Coen brother's version of the movie. I was surprised at LaBeouf's strong reaction against Quantrill and the Lawrence massacre, given that he's a former Confederate soldier himself ("I was in the Army of Northern Virginia"). I'm curious to know whether the movie is accurate in this respect.
Since they were basically on the same side in the war, why is he so hostile towards Cogburn? Was the Lawrence massacre so despised even back then that even people sympathetic to the south hated Quantrill? Was this a common opinion among Confederate veterans?
Also, I'm very curious about LaBeouf's reaction when Cogburn referred to Quantrill as "Captain Quantrill". What does he mean when he says "Captain of what?" I don't understand what he's referring to there, and why Cogburn takes so much offense at that line.
Any information to the background of that argument would be much appriciated.
It should be remembered that this is not just a line that helps situate the characters in the real world of the post-bellum period, but it is also narratively consequential, as it serves as an early character contrast moment between LaBeouf and Cogburn. So it's very intentionally playing up some real things for the sake of the story. And it's very effective from a cinematic point of view. Really well-done scene for a lot of technical reasons, including the writing.
That said, Quantrill's raiders really were a polarizing group in Missouri and the rest of the South, with some viewing them as 'well-intentioned extremists' while the majority probably considered them a cowardly and criminal rabble. Part of that was because of their embrace of guerrilla warfare at a time when such tactics were looked down upon in many circles, both military and civilian. Part of it was the fact that they really did kill children at Lawrence. And after that incident, the feeling among the rest of the Confederacy, and certainly the official stance of the Confederate leadership, definitely turned against them even further.
Quantrill really was granted a captaincy by the Confederate government, but continued to operate pretty much on his own and continue his guerrilla approach.
Since the Army of Northern Virginia, being so closely tied to figures like Robert E. Lee and Stonewall Jackson, became a somewhat beatified group during the evolution of the 'Lost Cause' mythos, the choice of this line by the writer is a very intentional way of rooting LaBeouf's character in a particular kind of image of the staid, respectable, genteel, and rule-abiding Southern man. It's the same reason the character is a Texas Ranger, a member of a famed and well-reputed official law enforcement unit (also, importantly, one under the flag and authority of a state, not the feds) and Cogburn is a rogue Federal agent at best and a murderous outlaw bounty hunter at worst; these backgrounds flesh out the characters for the benefit of the audience, in a storyline that does not dawdle with a lot of exposition or slow character-revealing moments.
The point is that this argument is drawing on this popular historical canon to create these characters that are at once very human and very representative of a cultural archetype. So would all regular Confederate veterans like LaBeouf have this view of Lawrence and Quantrill's raiders? No, opinions probably would have varied. But it could have happened, and thus it's not a particularly big leap of authorial fudging.
**Edit: never had gold before. Thank you.