Plot hole: When the bandits attack the pioneer's wagons they are chased on horseback by the Captain, Jack and others for quite a distance until Ennis is killed in the confrontation with one of the bandits. In the following scenes Elsa is mourning over his body but her mother and others from the wagon train stroll up and the wagons are in the background-all this after a fairly long chase.
Factual error: Horses tied behind Elsa seem to be wearing nylon flat halters that weren't invented until Feb 1894.
Answer: Tim McGraw (the actor of James) put it best. McGraw has explained that James has PTSD from serving in the war. It doesn't help that, per McGraw, James was forced to serve and did not actually want to participate in it. This would make the war not only a shameful memory for him, but a painful one at that. Especially during a time when therapy was not a thing and people, particularly the male head of the households, were taught to hold feelings like that back. In his suffering brain, he thought it was best to try to put that memory aside rather than openly talk about it.