Seinfeld said it best. Loyalty to a sports team is nothing more than being loyal to the color of laundry. Players change all the time.
Sports loyalty is a little weird if you step back and think about it because you are being loyal to a franchise of players, ownership, etc who don't care about you at all and and don't even know you exist. These teams will up and move if the taxpayers don't agree to being extorted to fund their shiny new stadiums.
I know more and more people who root for individual players and whatever team they play for ala Lebron James rather than for the team itself. Once he moves, they no longer care about that team. Fantasy sports plays a role in this, too. Rooting for your own interests of your lineups over your team's result. Or placing bets against your team.