This passage from Jim Caple's "The Devil Wears Pinstripes" describes, much more eloquently than I ever could, why I dislike the Yankees:
Sure, there is an undeniable pleasure in rooting for a team and in being able to look down on opposing fans with equal measures of superiorty and disdain. But that's also the Ruthian drawback in rooting for the Yankees (along with high ticket prices, overpriced concessions and crude neighbors). The true pleasure in sports comes not from simply winning but from watching a team overcome adversity to win in the end. The joy of sports is never the final destination, it's the journey. It's experiencing the highs and the lows, and appreciating those highs all the more because of the awful lows.
Yankees fans can't know that. Their team has been so successful, they are so rich and so stocked with talent, that anything less than a World Series victory is a complete disappointment. And by the same token, if they win, there is no real sense of accomplishment. ... Anyone can root for a team that wins all the time. The test of a real fan is whether you have the character to stick with your team through thick and thin.