I met a girl at Iowa who is from the burbs of Chicago, like me, who is a "fan" of the: Packers, Cardinals, and Bulls. Try to explain that one without sounding like a bandwagoner, you have a hometown (technically) team in every sport and yet your favorite teams are the defending super bowl champs, perennial WS competitors, and a team that had the best record in the NBA last year. Hard to believe you're truly committed to your team's outcome.
I had a roommate from Iowa who is a Raiders fan. That I can respect. He followed them pretty closely, they haven't been very good in a decade-ish, and he's from Iowa so it's not like he's intentionally ignoring his hometown team because they aren't good.
What annoys me about bandwagon fans is their opinion regarding teams, it's usually not based on personal observation. It's like they get all of "their" opinions from ESPN or the box score. They're usually confrontational in their rooting as well. It's not "Woo! Go team!", it's more like "Woo! In your face!"
I digress...