There's numerous scenes in the movie where he talks with or acts friendly toward Confederate prisoners - first with the Tennessee private from Archer's brigade ("fightin' for our rats", "see ya in hell Billy Yank") and then on Little Round Top with a captured Alabama captain (who asks for water). For as comparatively little focus as he had in the movie this seems like a lot of fraternization with the enemy for a commissioned officer like him, did he really do this or is this fabricated?