Eh, because playing international football is an honour you should have to fight hard for? If you're not good enough to play for the country of your (or your parents) birth, hard lines. Is James McFadden lucky he wasn't born in Italy because he wouldn't get in their team but is a key player because Scotland have fewer players to choose from? Undoubtedly. But that would have been his bad luck. This is why I have very little interest in international football. Sullivan, Elliot, Commons, these guys all devalue the whole thing.
Will I boo McCarthy on Saturday? Not unless he does something on the field that merits it. His choice of international team, while it saddens me, it only does so as a symptom of the greater malaise running through international football...