No, you don't. You do not have to so conclude.
Goldhagen is trying to understand why it was the case during World War II if you took a random German adult or adolescent male, gave him a gun, and had an authority figure tell him to "shoot those jews," the odds were better than nine out of ten that he would do so.
Finkelstein is saying that Goldhagen's argument is immoral because "moral culpability... presumes moral awareness." Thus: "Touted as a searing indictment of Germans, Goldhagen's thesis is, in fact, their perfect alibi."
But Finkelstein appears to have a crude, melodramatic, and silly view of moral culpability. Moral culpability does not merely attach to those who cackle as they slaughter, saying "Look how evil I am! Look how cruel I am! Look how immoral I am!" Moral culpability is--I think--much more often generated by a *lack* of moral awareness.
I must confess I never figured out what Finkelstein's argument was. The closest I could come to it was as follows:
--We must judge Hitler's willing executioners to have been morally culpable.
--Goldhagen believes that Hitler's willing executioners were not aware that they were committing horrible and immoral crimes.
--If you aren't aware that you are committing a horrible and immoral crime, than you cannot be judged morally culpable.
--Therefore Goldhagen is a bad person, because he is trying to prevent us from judging Hitler's willing executioners to have been morally culpable.