Why did Arthur Goldman impersonate Colonel Dorff?

The 1975 film The Man in the Glass Booth tells the fictional story of Jewish holocaust survivor Arthur Goldman. Thirty years after the war, Goldman impersonates an unrepentant concentration camp commandant, Colonel Dorff, allowing himself to be abducted and put on trial as Dorff by the Israeli authorities. Partway through the trial, Goldman's ruse is exposed by the witnesses he had bribed to present evidence against him. The normally voluble Goldman suddenly becomes catatonic and he dies in the courtroom without ever having offered an explanation for his actions.

What was Goldman's motivation for impersonating Colonel Dorff? I can speculate that it may have been one or more of the following:

Goldman had gone insane, perhaps as a result of the hardships he suffered under Dorff, and became so fixated on his former tormentor that he took on his persona. We see Goldman exhibiting plenty of irrational—possibly even psychotic—behaviour in the first half of the film, before he openly assumes the role of Dorff. And a psychiatrist appointed by the court to examine Goldman (albeit believing him to be Dorff) finds that he is suffering from psychosis. Then again, it's also plausible that Goldman was faking mental instability in order to set up and maintain his cover without raising suspicion. For example, at one point Goldmann instructs his employees to call certain numbers in Hamburg and Cairo and then immediately hang up, giving an apparently (to them, anyway) nonsensical explanation for this order. In the second half of the film he reveals, in Dorff's persona, that two of Dorff's former SS colleagues are living freely in Hamburg and Cairo.
Goldman wanted to draw public attention to Dorff's crimes against Goldman, his family, his fellow Jews, and humanity at large. Since Dorff had thus far escaped justice, Goldman felt it was necessary to expose him to the world, and the only way of doing so was to pretend to be Dorff and to flamboyantly confess to everything. This is certainly the interpretation that Star Trek: Deep Space Nine used when they reimagined The Man in the Glass Booth for their first-season episode "Duet", since Marritza, their version of Goldman, admits to this once his cover is blown. But there's no such catharsis in Booth, where Goldman dies without leaving an explanation.
Goldman wanted to publically berate himself and his fellow Jews for failing to stand up to Dorff and to the Nazi regime generally. Again, there are several parts of the film that hint at this explanation, such as Goldman using the trial to ridicule Dorff's victims as weak, the court frequently asking witnesses who were themselves camp survivors why they didn't engage in resistance, and, perhaps most damningly, Goldman's employee's testimony that "the man in the glass booth [i.e., Goldman, posing as the defendant] is a Jew" because "no gentile could ever be as antisemitic as Mr. Goldman is". Still, these are only hints.

Now, the film is extremely dialogue-heavy—or perhaps it might be better to say extremely monologue-heavy, with lead actor Maximilian Schell delivering huge numbers of lines on rapid-fire for almost the full two hours. Moreover, as I've mentioned above, many of his lines seem like throwaway comments or non sequiturs at first, but are revealed to have great significance to the plot much later on. It's possible (even likely) that I may have missed something in the first half of the movie that provides a more definitive explanation for Goldman's behaviour in the second half. Then again, it's also possible that the filmmakers intended for Goldman's motivations to remain obscure or ambiguous.

What I am basically asking is whether there is anything in the film itself which establishes an explanation for Goldman's behaviour as definitive, or at least more probable than the alternatives. Failing that, is there any evidence from the filmmakers themselves (not from Robert Shaw, whose novel was adapted but who completely disowned the film during its production), such as directions in the original screenplay, deleted scenes, or interviews with director, writer, cast, or crew? Again, I don't care what happens in the novel; my question is about the film.