Well, the diagnosis is incorrect. This is not Obsessive Compulsive Disorder, although there is an element of obsession about it. Think of it this way. Abu Ghraib symbolizes to the true anti-American paranoid everything they believe about America, American values and morality, and American evil. They are obsessed with Abu Ghraib precisely because they want it to prove that they have been correct about America all along.
One of the hallmarks of the paranoid, and paranoia in general, is the ability to fixate (or obsess) on one particular point to the exclusion of all other reality and to select that point as the "evidence" of their predetermined delusion.
The paranoid is actually quite perceptive--rigidly so; and they focus their attention only on those details that give support and credence to their beliefs.
David Shapiro, in his book "Neurotic Styles" comments on the Paranoid style:
In the paranoid person, even more sharply and severely than the obsessive compulsive, every aspect and component of normal autonomous functioning appears in rigid, distorted, and, in general hypertrophied form....[The]paranoid person's attention is so purposefully and narrowly directed as to amount, not merely to rigidity, but to a fixed bias.
Normal people are able to see things in context and their judgement is therefore more reliable and unbiased. The paranoid's pre-existing bias distorts his judgement and makes him unable to place facts or events in any appropriate context.
Note also all the conspiracy theories and deeply held conviction that the abuses exposed at Abu Ghraib are part of a massive government and military plot to deliberately commit atrocites and that the plot goes up the military heirarchy to the Secretary of Defense and through the Department of Defense to the White House itself. Of course, this belief pre-dates Abu Ghraib, but firmly became attached to that place when it was perceived that what happened there could be used to prop up the belief system.
So, we should not confuse this incredible paranoia concerning the behavior of a few misanthropes and sadists at Abu Ghraib, with the relatively milder preoccupations of an obsessive compulsive.
The treatment? Such people cannot be talked or reasoned out of their delusional preoccupations, because they are too central to their identity. Sometimes medication can help, but since they don't believe they have a problem, getting them to try it is usually a waste of time. There is very little insight and even less motivation to change, since reality would be too threatening.