Embassies are especially fair game (outside the grounds and in a safe fashion) . A protest in private is no protest at all.
So when the taliban make it illegal for women to go to school, citing the Quran….While I don’t think fire is the right thing to do, I absolutely agree it is a right to burn shit somewhere in front of the afghan embassy. If that includes a flag or religious text owned by the protestor, so be it.
However, people have the right to physically gain access to the buildings of use (service, home, food, etc) and safety first. Blah blah blah.
In general, the state should read public protest as a sign that local democratically elected officials are not aligning with the values of their constituents.