Howard W. Campbell, Jr, is writing his memoir as he sits in an Israeli prison cell, accused of war crimes in Germany during World War II. If you believe Howard W. Campbell, Jr, he's guilty as charged, but he's the only person whose direct testimony we're given. He surely was a high-ranking Nazi propagandist; he might have been an American spy. Certainly, some Americans seem to have conspired to protect him from war crimes charges at the end of the war, but even the man who recruited him as a spy doesn't seem to think his great service to the allied war effort makes up for the damage he did as a propagandist. On the other hand, the Israelis seem willing to acquit him if only he can prove the existence of the spymaster.
Throughout, Vonnegut dances around the questions of what a person's moral duties are in a time of worldwide insanity. We'd all like to think that we wouldn't be the people who helped send Jews to Auschwitz, but would we be able to stand against such insanity? Certainly Vonnegut has no interest in telling us either where the line between good and evil should be, or on which side of the line either author or readers stand.
In the end, Howard W. Campbell, Jr. seems to consider his death the final touch in his propaganda campaign. So it goes.