Not everything needs nor desires a deep well thought out intellectual response or witty comeback. I'm not justifying what he said, but at the same time he was

Not everything needs nor desires a deep well thought out intellectual response or witty comeback. I'm not justifying what he said, but at the same time he was just letting off steam. In fact it's possible he felt bad about it later (or not). What I would of done in that case is just to try to be friendly with the guy and talk to him about stuff not related to the situation at hand. He is stressed out. I used to suffer badly from similar symptoms as described in the OP (although not as bad, so I can't relate perfectly). But over the years what has helped me is to focus less on myself (how do I feel, what is he/she saying about me) and more on the other person.