Normally, if "my team" isn't in the post season, I just don't give a crap. In baseball, it didn't even bother me that the Red Sox won a couple of World Series over the last decade, despite the larger percentage of the fans of that team act in a classless way - instead of savoring in their victory, choose to utter such infantile nonsense as "the Yankees suck", etc.
I have a lot, I mean a lot of friends who are Red Sox fans. And I can tell you that there are good people that are Red Sox fans, I know this for fact. Sadly, in my experience, it's not the larger population of Red Sox, and Boston sports fans in general.
I've seen Red Sox fans at Yankee stadium be incredibly disrespectful and classless, I've seen Red Sox fans literally beat up Yankee fans at Fenway whose ONLY crime was wearing a Yankee shirt and cap (not yelling bullshit); this is unacceptable behavior.
I've seen riots, where "excited" Boston sports fans set fires in the streets, turned over cars and buses and caused hundreds of thousands of dollars in damage as a result of their "celebration". This almost never happens in any other city when a team wins, the celebrations are civil and life goes on, even Detroit was civil when the Tigers made the post season. I can't and won't condone that ridiculous violent behavior.
It's just fine to love your teams, it's just fine to be passionate, it's even okay to hate the arch rival - but have some human decency, dignity and be civil.