It's a pretty mindbogglingly difficult situation, to be sure. But don't get too hard on all of the cops and all of the looters.
The cops are badly overstrained. According to the mayor of NO in an interview this morning, it was only last night that the whole force was put on civil control rather than rescuing people. That's a pretty nasty Sophie-esque choice. Do you rescue people in desperate need because of the flood, or do you try to assert public order (which is, in a way, another version of saving people but from a different problem)?
And with the looters, there have been plenty of reports of people looting for necessities as well as the more opportunistic ones just stealing stuff. Some of the people brandishing guns at the security forces have been demanding that they go and rescue their families. Some people are doing it out of desperation, absolute desperation and they aren't thinking straight.
There's also a lot of conflicting reports about how widespread the looting and rioting is. NBC was a bit dismissive of it because their news people have been able to get around the city without any personnel difficulties. They've been reporting that some of the evacuation and supply vehicles had been holding back out of fear of being attacked by looters, perhaps in overreaction. So I'm not really sure about the magnitude of that problem in general. Chances are it's a set of highly localized issue or randomly roving and thus not pervasive.
What I worry about most is all of the small children. Babies dehydrate like crazy because they have fast metabolisms and they sweat a lot (especially in NO weather). Maybe it's because I'm a father myself (kids are 7 and 1) but this sort of thing affects me a LOT. Hell, my heart still goes out the families of the kids taken hostage (and many killed) in Beslan a year ago. There are just too many bad things in this world, both man-caused and natural, that make me want board up the house and not let the kids out of my sight. But I know that odds are on their side and they'll probably do just fine... I just wish the kids of NO were as lucky. I hope most of them turn out to be so.