Normally, I consider it a positive attribute to be able to see the world in shades of gray. It's rare that anything's clearly one way or another. There are always several sides to most arguments, and I often bristle when people try to reduce the complexities of a debate down to a single mantra, slogan, or viewpoint.
That's why I love sports. It's one of the few things in life that's black and white. You win or you lose (ties are like kissing your sister). You score more runs/points/goals: You win, and everyone's happy. You get beat on the scoreboard: You lose, and you feel shame. But there's always a next game waiting, and you might win that one. Unless you're a Raider fan.
Being a sports fan is also very cut and dried. You root for your team, win or lose. You don't switch in the middle of the game when your team starts losing. You put up with lots of losing in the hopes that one day you'll be rewarded with your loyalty.
And one more thing: You root for the team that plays in the city nearest where you're from. You don't get to pick and choose. You don't get to throw darts at a board. You just don't.
This seems like a stupid, arbitrary rule. But that's the thing about sports: they're stupid and arbitrary. That's why it's easy to have a black-and-white set of values to abide by. Ultimately, we're all just "rooting for laundry," as Jerry Seinfeld puts it. There's no nuance to this. You grow up in an area, you root for the teams from that place, no matter how badly they may suck. You'll have some good years and some bad years, but no true fan abandons his or her roots in search of greener pastures.
There are only three exceptions to this rule:
1. Your parent grew up a huge sports fan in another area, has since moved, and has indoctrinated you as a fan of his childhood team. Sports fandom is like religion; it's passed down to you, and there's not much you can do about it. Unlike religion, which is actually an important life decision which should be based on careful study and personal beliefs, you don't get to change because your current team's performance isn't satisfying you. Again, this may seem stupid and rigid, but that's the code of sports.
2. The team you grew up rooting for moved away. You are now not beholden to them and may pick from any other team. There is a caveat to this: the more historically successful/popular a team is, the more douchey it is to pick them as your team of choice. Anyone can root for the Lakers, the Cowboys, or the Yankees year after year; it takes someone with cojones to randomly choose the Houston Astros, Seattle Seahawks, or Columbus Blue Jackets. Coincidentally, I've never known anyone from L.A. who was a Clipper fan or raised their kids as a Clipper fan. Always the Lakers. I'm sure it's solely due to the fact that the Lakers were there first, not because L.A. sports fans are largely frontrunning bandwagon posers who can't even support a football team.
3. You grew up in an area without a pro team anywhere nearby. Montana, Hawaii, Mississippi, etc. You are also a free agent. See #2 above.
There are no other exceptions to this rule. You can't say stuff like "I just really like Shaq, so I pull for the Lakers." It's fine to really like Shaq, except when he's playing your hometown team. Then he's the enemy. I was a huge Barry Sanders fan growing up, but when the Lions played the Niners, I wanted S.F. to shut him down. Ditto Tony Gwynn, Kirby Puckett, Mario Lemieux, Kevin Johnson, etc.
It doesn't make any sense to root for a team just because a player you admire toils for them. Players move around all the time. Even in the rare cases when someone like Puckett, Gwynn, or Magic Johnson plays his whole career with one team, that's just the luck of the draw. If that player had been drafted by someone else, he would've played just as hard for that team. Kobe Bryant is the notable, petulant, rapist exception that proves the rule.
Players don't care about what color the uniform is they put on. They play for money first and competitive glory second. Fans are the ones who care about the name on the front of the uniform; the players worry about the one on their backs.
Again, we're rooting for laundry. But there's honor in that. I wrote before that the rules of sports fandom are silly and arbitrary, but allow me to give a rationale for the idea that one should root for his or her local team exclusively.
Sports bind a community together. It's a common touchstone we can all share. When things are bad, we commiserate. When they're good, we are hopeful and optimistic. When they're great (which hasn't been for a while now), we hug total strangers in bars and experience a kind of communal euphoria.
Even within the community, there's diversity. Each fan base develops an identity. There's the eternally hopeful and knowledgeable Warrior crowd, the equally hopeful but increasingly nonexistent A's patrons, the proud but unsatisfied Shark followers, the sophisticated Giants crew with their blackberries at the ready, the Cal fans who absolutely know that the next disaster is around the corner, even as they hope against all hope for the best, the wine-and-cheese bourgeois Niner fans who mix easily with the fading blue collar San Francisco element, and of course the unwashed Raider masses, with their felony convictions and ref-hating paranoia.
For as much grief as I give Raider fans, at least they're loyal. I would much rather talk sports with one of them than a lifelong Bay Area resident who professes to love the Lakers. Because that person is not a real sports fan. Oh sure, those "fans" may get happy when their adopted, far-away team wins and dejected when they lose, but it's not real. It's not earned. It's not respectable. It's a cop out. They might as well be rooting for another region's weather.
A huge part of being a fan is giving fans of another squad grief. When I find out that someone's breaking the rules of fandom by rooting for a team he or she has no right to, I instantly break off the conversation. Because the person just doesn't get it. You want to talk smack to me about a team you chose because it's successful, while I put up with the Giants' woes (and lack of a single championship) year after year, and act like we're fan equals?
No, we're not. Now shut up.
"But I've always liked the Lakers/Cowboys/Yankees! I'm a true fan!"
No, you're not. Now shut up.