If the PA can't control Palestinians within the confines of Gaza, how can they be expected to control them in the wider area of the West Bank? Sharon has given the clearest possible demonstration of the intractability of the foe and of the PA's inability to govern.
That is precisely what Sharon knew and why he continued the building of the fence/wall, then announcing that all of the territories would be vacated with Israeli's forced to leave and move into ground that Israel is prepared to defend.
The U.N. and other terrorist organizations have always claimed that it was Israeli "Occupation" of the ground that they fought and died for in 1967, as the reason for the Intafada but the real reason is as it always has been - to wipe Israel off the face of the map, as the Palestinian maps used by the school children show no Israel there at all.