Self-irony is indeed important. I think another purpose of seemingly insultive humour is to really connect:
About then years ago I met a guy during work, we drove together during the early shift and each morning we greeted each other with a weird insult we picked up during work. When I meet my best friend we sometimes do something similar, greet each other with some kind of half-insult.
The purpose is to signal that one is beyond this distanced politeness, that we can insult each other because we are buddies. When you have fallen in love and not realized it yet consciously something similar can happen, you tease or insult your beloved precisely in order to get out of this deadlock of distanced politeness.
I think your ethnic jokes about West Virginia work similarly. We insult each other or ourselves to signal that we are beyond political correctness (which is precisely why I cannot stand it, it is officially about tolerance but actually quite intolerant: don't come too close, get away from me, I do not really wanna connect with you unless you are a sterilized version of yourself).
Last edited by horatio : 07-28-2012 at 12:44 AM.