Lots of things are sacred. What else shall we add to your exemption to the First Amendment?
The Constitution is far more important to me than any other symbol of our nation. Shall burning it be prohibited?
The Bible is sacred to many people on these boards. Shall burning it be prohibited?
The Torah is also sacred to many people on these boards. Shall burning it be prohibited?
The Koran is sacred to many people in this country. Shall burning it be prohibited?
While we're on the subject of flags, my cousin died under the flag of the US Navy as well as the US Flag. Shall burning it be prohibited?
Where does this end? Why some symbols, but not others? What's your logic?
Shall preventing burning it be prohibited? Why is that opinion any less important?
A flag burner says, "No speech is more pure than my burning a flag in public." If that's so, then certainly the converse is true: no speech is more pure than acting to prevent the burning of that flag in public.
They are two perfectly complementary sides of the same first amendment coin.
You are arguing that only side should be recognized and that government should punish anyone who disagrees. That assigns a higher value to the flag burner's speech. That is neither just nor right.