Your assertion that the relativly small city of New Orleans was disarmed in the aftermath of Katrina is ... until proven otherwise.
Video from Katrina.
http://www.youtube.com/watch?v=Zztaj2AFiy8
Articles discussing the gun confiscations and lawsuits.
http://www.freerepublic.com/focus/news/2336066/posts
http://www.nraila.org/Legislation/Read.aspx?id=4205
http://volokh.com/posts/1153899155.shtml
http://blog.nola.com/updates/2008/10/nra_to_settle_suit_over_katrin.html