This is something the negative activists across the political spectrum need to understand

If you set fire to your own car, film it and post it to YouTube to protest climate change you are perfectly within your rights.

Setting fire to other people's cars is going to get you arrested and rightfully so.

If she bought her own flag, set fire to it, and posted it on YouTube she would be perfectly within her rights and the government couldn't do anything about it.

However setting fire to someone else's flag that is attached to a building is arson and potentially attempted murder.