I remember reading in Flex about how he was shot (in the leg?) when he was in vietnam, and that he had to literally play dead while lying on the ground. All of the soldiers were going around and stabbing the bodies to make sure everyone was dead. Robby had to lie there, knowing he was about to be stabbed, and not make a sound or move a muscle, otherwise he would have been killed.
If true, its not hard to see why this guy is insane. Can you imagine having to go through all that?
It would fuck you up beyond all recognition.