From what I've seen and come to understand, many of the folks who did not evacuate were handicapped or elderly or both. It also happened a few days before the fixed income folks got their checks :-( To confound the situation, many of these people had been "lucky" many, many times before when told to evacuate (although I believe this was the first time that evacuation was mandatory) and most of the previous hurricanes skirted the city or missed it entirely. Add to this a dose of cajun/creole independence and you have a major recipe for disaster.
I 100% agree with your statements. Having lived in New Orleans, I saw what a political football rebuilding the levees had become. "If we rebuild the levees then there will be no extra-curricular activities, etc." Local officials screwed this one big time through short sightedness and absolute denial.
You can forget what a bunch of crackers and black bigots say that have never been to the city (and even ones that have been there that have a black/white, demo/repo agenda). They are trying to politicize this disaster. There is a racial component to this, there is a socio-economic element to this, but it is actually just a fulfillment of what evey geologist and urban planner had been predicting for the last 70 years. New Orleans politics, plain and simple, doomed this town and it's poor to the current state. FEMA was late, the National Guard was late, but New Orleans/Louisiana politics was a complete no show. Where is the state capitol of Louisiana anyway? Oh yeah, an hour away...