I think the reasons behind this guy’s behaviour have more to do with personality rather than environmental conditioning in the military. I spent many years in the army and encountered numerous individuals who just would not have fitted in anywhere else. They weren’t a product of the army, but the army did give them what they couldn’t get, perhaps, elsewhere; status, authority, uniform, power, respect of subordinates etc. Sooner or later, the army has to return them to society and they hit the ground with a thump. My advice is to just pick them up gently and point them in the right direction. They are inherently inadequate and need support, in some form or other.