Pretty clearly the sweep by the Dixie Chicks was not to reward their musicianship. It was meant as a poke in the eye to President Bush. And the continued boycott of them by country music radio is about making a statement of values by those people. Pick your politics, and make your choice.
But it's not about the music anymore, which is too bad. It might be impossible to even think of the Dixie Chicks -- buying their albums or not -- strictly in a musical context. If they fade away, that will be why, not because of their specific politics.