In other contexts I would burn a flag, sure. The flag is emblematic of the struggle that is our country, and the struggle can mean different things, positive and negative, in context.

At the end of the day, we all live in America. We have an idea of America as a multi-cultural, immigrant nation. That is the correct idea. We have a right to define what the flag means.

Otherwise we've already conceded the patriotic high ground. It's like giving the enemy control of the (metaphoric) capitol of the nation just so we can be the insurgency. You feel better but it's tactically irrational. Why is it not better to start out with moral ownership of the nation's core symbol?