Max Blumenthal nails it in his report on Louis Farrakhan's remarks in which he cites radio talk-show host Hal Turner as a source of his information regarding Turner's conspiracy theory that the New Orleans levees were sabotaged.
Be sure to read it all. I'll just add this: Why anyone would want to be associated with Farrakhan in any fashion -- let alone partipate in an event designed to burnish his reputation -- is beyond me. Whatever good the Million More March may achieve (and as Max says, its larger purpose was truly laudable), his involvement will always cast a cloud over it.
For a little more on the execrable Turner, see this, this, and this.