The kicker is an essay tacked on to the end. Noting the excessive anality, homoeroticism, and fetishism of the Nazis portrayed in the book, Whipple points out the impossibility that a demented racist view like Hitler's could be accepted by a modern nation, and actually become realized. This is Spinrad's overt thrust, being the insanity of the whole Nazi episode, and the lingering question of why the Germans let it happen. There is a more important, unstated idea. A close reading of many popular titles forces us to ask why we put up with space opera and military sci-fi tropes that revolt us when we consider Nazi history.
Literature is a perceptual exercise, and creating monsters is a small perceptual leap.
The reader only uses what the writer presents. Genocide against evil is an accepted archetype of sci-fi and fantasy. The fly in the ointment is that evil is not necessarily an objective condition, but a subjective condition defined at some level by one person or a group. Genocide against evil is, at its root, merely genocide. And literature is much like propaganda.