So flags shouldn't be burned for the same reason we don't allow people to spraypaint on national monuments? I don't see the link. I'm not allowed to spraypaint on my neighbor's house either, but that's not because it's a national monument. It's because it doesn't belong to me. Spraypainting a national monument is illegal because it's the defacing of property that isn't mine. But if I buy a flag and set it ablaze, I'm burning my own property, and thus is a completely different situation.
Perhaps we don't buy flags - we only rent them?
LXN