Thats poor taste on his part. He is a good baseball player, but thats disrespectful. In a game which has many roots in American History, historically has not put up with any non-sense from players and suspended those who make the game look bad, he should suck it up and get out there. Showing a little respect to the game, its fans, and the country that's giving him the big bucks. Otherwise there are other options such as playing baseball in Japan or Puerto Rico, good luck making that much money in either place...
Its similar to kids in schools (or citizens anywhere for that matter) that don't stand for the pledge of allegance. They bitch and moan about free practice their rights, but don't have an ounce of respect for the country that affords it to them. Don't like it, tough...deport them to a repressive Middle East, Asian, or South American Country. Anywere else you would follow the rules of the respective society and not dare to balk or disrespect the people and their culture.