Nietzsche liked the Sophists for their anti-authoritarian stance, their championing of rhetoric, and their opposition to the dogmatic thinking of the Socratic schools.
He says subsequent generations have come to see them as immoral after seeing the hate piled on them by Plato and his gang: "for now we suspect that it must have a been a very immoral culture, since Plato and all the Socratic schools fought against it!" (Daybreak)
Nietzsche demonstrates (unknowingly, I think) a Buddhist appreciation of the Sophists when he praises their ability to engage in agons of rhetoric that chalenge the notions of a permanent self. Self, morality and desire are all conditioned states that need to be contested on a continuous basis.
As usual, Nietzsche rocks.
Brian