The Dixie Chicks and everyone else is free to say whatever they want
And the consumers are free to make their purchasing decisions as they want. People decide to buy (or not to buy) things based on very personal criteria. If someone decides not to buy a CD, concert ticket, or movie ticket because they were offended by the celebritites involved, then they're free to do so. The celebrities still have the same freedom of speech as before but perhaps they'll have a little less money.
Likewise, other consumers who agree with the celebrities might be more likely to buy their products. Imagine that, consumers making individual purchasing decisions in a free market. What a concept!