I had a really shocking and disappointing experience a few years back.
It's a Friday night here in Va Beach, and my fiance and I are out for drinks and to shoot pool. We're at our local Steelers Bar, and the Steelers preseason game is on (can't remember who we were playing). Anyway, one of the guys in the place (probably in his mid 20's) starts yelling at the TV, Steelers Suck! You all SUCK. So, I leaned over to the bartender, and asked her if the guy had any idea what kind of bar he was in (not that it's hard to miss...there's Steeler's stuff everywhere in there). She told me that she had known him for awhile, and (get this), he was BORN AND RAISED IN PITTSBURGH AND HE WAS A PATRIOTS FAN!!!!
I couldn't even look at the guy from that point on. I mean how can you grow up in Pittsburgh and not only not root for the Steelers, but root for the PATRIOTS?!?!?!?!