This piece from Cheryl Bernstein encapsulates the arguments against wholesale heritage destruction far better than I could. Highly recommended reading.

I’m an art historian because I know that historical art brings the past nearer — art is, like cinema, a time machine — and because I believe that contemporary art has something to tell us about the present and might, at its best, reveal a new way of looking at the future. When the Minister in charge of earthquake recovery, Gerry Brownlee, says that “heritage is both forward and back” he is absolutely right. But when he says that — apart from a few civic buildings — the heritage buildings which remain “have no place in our future history” he is demonstrably short-sighted. Demolishing our history offers no useful solution to the fears of the present day. Without the material presence of the past we are cut off from our collective memory, and there is worse danger in forgetting. Like the world of speculative fiction, the everyday world is capable of sudden and violent change at any point and the more information we take forward with us from the past the better we are equipped to deal with the great and certain strangeness of the future.