I haven't seen The Fog of War, but I have watched several interviews with McNamara, so I think I have a pretty good impression of what he says.
What is interesting to me is the idea that some how Robert McNamara and the United States government were the victims of Vietnam. According to this surreal and exculpatory inversion, the mass slaughters and devastations that collapsed into a nightmare of utter meaninglessness were not the consequences of deliberate policy, planning and orders. Instead these catastrophic horrors were some how a product of nature that condensed out of the fog of historical circumstance, as if it were all a mere phenomenon. Once manifested, these events were underway of their own volition, and there was nothing that could be done, but to attempt to guide the course toward the most humane outcomes. The tragedy then consisted in the inability of the captains of war to find and steer this humane course through the miasma that followed. Thus the tragedy and failure was in the steerage alone.
This is the core of the revisionist history of Vietnam. It comes down to excuse that `she made me do it.'
Chuck Grimes