You have the right to yell "fire" in a theater, however if there is no fire, you are also subject to legal penalties for putting people's safety at risk by creating unnecessary panic. Burning a flag on your front lawn is not the same thing. You don't have the right to shun things that offend you.Would it be possible to enact something on the order of not allowing someone to yell "fire" in a theater?
Edit: For the record, I think flag burning is idiotic, but people have the right to be idiots as long as they aren't harming others in the process.