Laura Ries lays out the PR/Branding errors that the Dixie Chicks have made by being politically controversial. This mistake is a doozy:

The Dixie Chicks are a country act. Crossing-over means more album sales, but can leave you stuck in the mushy middle. Core fans think you have sold out and new fans can quickly move on to the next thing. The Dixie Chicks today are wearing lots of black eyeliner and saying things like “Country listeners are a bunch of rednecks; we don’t need ‘em.” Not a good move. Always remember where you came from and never insult the fans who made you successful.

Yes, publicly insulting your core audience is not a great way to move the ball forward - the audience is, after all, the source of revenue :)