Answer:
This situation is a very complicated one. The burning of the flag is disrespectful to the United States and it did injure two people. Under the first amendment, citizens have the right to peacefully protest and the right to free speech. So, technically the people are free to burn flags if they wish to do so, but this situation caused harm to others, so it is not a form of peaceful protest. Personally, I believe that these citizens have the right to burn as many flags as they wish but they shouldn't continue to do it in a way that may inflict harm upon others.