Haa!!
I know the feeling all too well. In 1993 I was at a Raiders v. Chiefs game which was the last game of the season, winner goes to the playoffs, loser goes home, situation. I went with my brother (Fayduh fan) and we sat up in the nose-bleeds of the Colliseum. As an official Raider-Hater, and someone who was a very big fan of Derrick Thomas, I felt inclined to cheer for the Chiefs.
To make a long story short, it was a back and forth game so not many people payed attention to me but the fourth quarter rolls around, Raiders are down by a couple but get down to the Chiefs 4 yard line and have all of their downs. First play, the QB (I think it was Hostetler) rolls right, tosses a little lob pass to a seemingly open Tim Brown in the end zone and, out of nowhere, a DB pops up and INT's the pass. He downs it, game over, Chiefs go on to the playoffs.
Before I knew what I was doing, I jumped up, starting pumping my fist in the air, and cheering. It didn't take me too long to realize that every eye within about 50 seats in all directions were on me. At this point I slowly shut up, sat down, and remained quiet until several of them had shuffled out of the gates.
I swear I saw my life flash before my eyes for a brief moment as hundreds of brain-dead, neanderthal, Raider-fans in the nosebleeds stared at me with enough hatred to make me feel like POW in a Nazi concentration camp.
The point of all of this was to say that I will definitely be careful. Hopefully I can hook up with a couple other 'Fin-fans so I'm not alone. :)