he sounds like he's really insecure and craves attention.

maybe the next time he gets hostile with you, say something neutral like, "yeah, that's interesting" and then address the group as a whole instead of speaking to him directly. this might initially infuriate him more, but if you silently remind yourself that he is a sad, cowardly man-child and wait it out he should become too tired to bother with you and move on to the next person.