Why Did God Destroy New Orleans with Hurricane Katrina?

Many people believe that God was real angry at mankind and got a wild hair up his butt and sent Hurricane Katrina into the Gulf Shore and New Orleans to teach people a lesson. But if that were so what was the lesson? Hard to say really and if it was a lesson did the little humans learn anything? It appears they did not.

Humans in their ultimate defiance are rebuilding the city under sea level as before and carrying on with Marti Gras as if nothing ever happened. Thus saying in affect you can