Simple.
There have been reports of bodies ridddled by bullet holes and bodies with heads blown off. More than likely they are white people.
The mayor and the National Guard may sense that the anarchy will INCREASE as long as white people are seen. After all, you have black "celebrities" on national television saying that "Bush does not care about blacks".
It is a correct call to make to get the whites out first, if the mayor and the security beleive that anarchy is rising and whites are the target. They need to eliminate the anarchy first so the evacuationa can continue.(Those members of the black ping list know that I am not white).
A good thread to read, Freepers at their best, with many of the answers.