To respond to a theme in this thread: why do people destory their own heritage?

"Heritage" has and always will be the product of a small elite ruling class. Think about it: the stuff that most people make and live around each day is rather unremarkable. A straw mat or a clay pot will look pretty much the same anywhere and any time in history. But give that as a reason to the owner of the pot you just smashed, and it will not fly with him.
Possession is nine-tenths of fondness for an object, so most members of a culture do not naturally have an emotional connection to the precious artifacts of their culture. With the exception of the children of the elite who literally grow up around the stuff (which is to say, what we could call "precious" is their "mundane"), a person's "heritage" must be taught.
In other words, precious artifacts mean the most to the elite that created them. They use them and display them as symbols of their authority. They teach the masses that support their empire to identify with these symbols - even to love them.
Now, none of this means that these artifacts aren't significant in a larger "human" context. Objectively, they are some of the finest things we as a species have produced. In some sense, they belong to all of us. But in truth, they only ever belonged to their progenitors, like a limb to its body.
So, when an Iraqi loots the dowry of some dead Babylonian princess, we musn't look at him as a cannibal turning on his own kind. He is more like a scavenger or a bacterium. Horrible, yes, but understandable.