The definition of fandom is bias. I'm biased towards my team, sue me. I reserve the right to declare Damon a traitor, not for leaving for more money, but for going to the Yankees. Maybe it was unfair of us to trade Arroyo after he took a discount (although realistically, how much more could he have really gotten?).
Baseball's a business, sure. But if Steve Jobs were to quit Apple and sign with Microsoft, wouldn't a lot of people be upset or at the very least confused?