What shapes your opinion of opposing fan bases?

[damaniac]

I've been thinking about this lately with the OSU game coming up. As a Michigan fan, I've been to Columbus and completely hated the experience and most of the people I came across. However, I've been only once, whereas the message board I hang out at has a few Buckeyes, all of whom are very reasonable and intelligent people. Conversely, my trip to Notre Dame was perfectly fine and I loved the place, but my main source of exposure to ND fans is ndnation, which is easily the worst message board in the history of the internet (unless everything posted there is a parody). So I tend to view Domers as irrational self-absorbed dicks, even though anyone I've ever met in person has been a total class act.

The correct classification of ND and OSU fans aside, what shapes your image of fan bases? Actual experiences at games, friends you have, images on TV, or internet message board discussions? Other?