Emphasis on the "some" part. The Boston Globe interviewed up to six sociologists and other social boffins and they say that after most natural disasters there's relatively little looting. They question whether there was as much looting after Katrina as the networks and the rest of the MSM have claimed.
From "Up for Grabs":
...[Clark McPhail, emeritus prof. at UIUC] says, that crowd you thought was ransacking Wal-Mart for consumer goods no doubt included people who indeed were ransacking Wal-Mart for consumer goods. But there were also mothers getting diapers, thrill seekers checking out the action, people trying to persuade their friends not to loot, and others just milling about...
Tell it to the judge! Oh, just kidding.
The article also contains this:
True, not all disasters have nonviolent aftermaths. After Hurricane Hugo swept through St. Croix in 1989, leveling the place, residents cleaned out local stores and malls, even going so far as to remove the lighting fixtures. What made St. Croix different from Kobe, Japan following the 1995 earthquake or San Francisco after the quake of 1989? [Enrico Quarantelli, an emeritus professor of sociology and the founding director of the Disaster Research Center at the University of Delaware] argues that it was the radical inequality of a society where yacht-owners live beside subsistence-level workers, the sheer desperation of the situation (citizens were stranded with no food and no expectation of rescue), and a corrupt police force.
Of course, these conditions were all present to some degree in New Orleans. Yet Quarantelli, Tierney, and other scholars give the benefit of the doubt to the Louisianans, discounting, until they have proof, much of the reporting of a social breakdown...
Until I have proof, I'm going to assume that those scholars have so much invested in "liberalism" that they're now seeing what they want to see.