Read these 4 urban legend posts on Snopes.com:
E-mail written by a paramedic details conditions in New Orleans.
E-mails by a volunteer relief worker detail behavior of New Orleans evacuees.
Evacuees verbally abused volunteers trying and trashed a rest stop in Waskom, TX.
Evacuees brought to Utah arrived bearing drugs and guns and immediately proceeded to sell drugs, attempt rapes, and rebuild street gangs.
All four posts purport to be eye-witness accounts of the relief effort after hurricane Katrina; all 4 go out of their way to demonise African-Americans victims of the disaster as greedy, ungrateful rude and violent. All appear to have spread far and wide over the internet. And all four are of doubtful veracity (Snopes scores two as false and two as undetermined).
To my mind some, if not all of the posts sound as if they were written by the same person. All of which adds up to an interesting propaganda campaign IMHO ...