I think what was largely missed above, was the extent to which people and programmers had a backlash against the Dixie Chicks. The ladies claimed death threats, for speaking out against a political leader. Oddly, we entered war in Iraq under the guise of searching for weapons of mass destruction, and Dick Cheney and others in the administration claimed 'we would be greeted as liberators'. Yet, on the home front, almost anyone who spoke out against the war (the Dixie Chicks, Michael Moore, Bill Maher, etc) were ostracized. Didn't we go to war in Iraq to liberate?
Rational people, regardless of which side of the political spectrum they're from, realize that an overreaction to someone questioning political authority and exercising their free speech, makes us no better than those from whom we claim we are trying to liberate others from in the Middle East and other parts of the world.
So, yes, fans have every right to stop listening to or buying Dixie Chicks albums, or even protesting at their concerts, but death threats and equally low brow forms of intimidation makes us look foolish to the rest of the world and are a violation of our own principles.