Regarding Flag Burning
If I go to the Post Office and take down their flag and stomp on it and kick it and inadvertantly allow it to become stained with urine and burn it; I would expect to be arrested.
If I go to Walmart and buy my own god-damned 'made in China' star-spangled banner I can do anything I want with it. Burn flags now. Glue them to the streets where they will be destroyed by traffic. Wear them on the soles of your shoes. Draw them on the sidewalk where they will be erased by pedestrians. Put vinyl flag stickers in urinals. Be sure to wash your hands afterwards.