No it is not just a piece of material. No more than the constitution and the bill of rights is just a piece of paper.

And yes you should have the right to burn it but when you do you should also be prepared to have your face punched in by those expressing themselves on your face.

I wish just once a gust of divine wind would wrap a burning flag around one of those idiots and disfigure them for life. They can explain to their grand children how they got their scars.