Continuity mistake: When Cortez gets out a photo of his wife pregnant, the photo changes between shots. She is facing a different direction in the next shot. His USMC tattoo, however, stays the same direction throughout the scene. (00:26:55)
Continuity mistake: After the Christmas party and the fireworks blowing up, Swofford is seen sitting at a table drinking Crystal Geyser spring water and talking to Jamie Foxx. Between shots the front of the bottle keeps moving to continually show the Crystal Geyser logo facing the camera for perfect product placement.
Continuity mistake: In the scene where Swofford is threatening to shoot Fergus, in all the frontal shots we see that Swofford's face and ear are touching the end of the rifle. In all of the shots from behind, his face and ear are no where near the rifle. There isn't enough time for him to move the rifle away from his face between shots.
Answer: He was just an old former Marine (I would assume a Vietnam vet) that wanted to congratulate the Marines, and give them a better welcome home than the Vietnam vets ever got.
EMTurbo