There are def a lot of bandwagon fans. Last year I kept getting killed by my mates for my undying love for the Celtics. The thing though is that throughout the years I have def met and bonded with fellow hardcore Celtics fans. We can differentiate the fair weather with the hardcore and we can appreciate their support.
For example, the other day I was going to a bar in Boston and saw one of my neighborgs in college that I hadn't seen for 1-2 years. He was one of the guys that I used to watch Celtics games with. Anyway, he sees me and the first thing the both of us thought were, how about them Celtics!
It has also happened with other people. Guys that I know are diehard fans. No matter what happens, regardless of when they;re playing well or not, I can always start a conversation about the Celtics and know they're right on top of things.