This is why I hate major league baseball. But I suppose it's the same for all professional sports. It's as much about business as the games played. Look at the NBA. When they make a trade they don't really exchange players but dysfunctional contracts.
Yes, it's a ruthless business when you trade your most popular player to the league's most hated team. Where Curtis Granderson became a luxury the Tigers could not afford the New York Yankees see him as a low-cost solution to their need to get younger, have more speed and maintain their lefty power hitting.
In a parallel universe maybe Granderson finishes his career with the Tigers and adds his name to the greats who spent their whole careers with the team. Based on the outpouring of emotion that followed news of the trade, a lot of Tigers fans would have preferred that ending. Now Granderson gets to be a New York Yankee and spend at least the next three years chasing World Series Titles.
Mack Avenue Tigers said it best about the trade and Granderson, "...It's a bit like putting your girlfriend on a bus to Hollywood, as she leaves you to try to break it big in movies. I'm happy for him to get that opportunity, but ... he was ours, and kind of a big deal and important figure in the state of Michigan."
I live in New York City, and hate the Yankees, but to see and hear about them all the time you need to have a game within a game. Players you love to hate and players who though they may be Yankees are not so bad. It'll be nice to follow Granderson as he takes his place in the Bronx.