He was apolitical, he had no interest in anything but getting into space. He joined the Party to simply advance that goal, and if his publicists are to be believed, he was, at best, a lackluster and disinterested member of it. I don't think the Nazis "perverted his interests". I think he took advantage of them for his own purposes. He would have gladly worked for the Communists if they had put him in charge of their space program.

His decision to defect to the allies was strictly a practical one: he knew the West was less likely to enslave him, or kill him on the spot. By that stage in the war, all Germans knew perfectly well the kind of war the Wehrmacht had inflicted on the Slavs, and they were perfectly correct in believing their former victims were eager for a grim revenge. They also knew that slave labor, and worse, actually produced the weapons because the quality control problems created by worker sabotage in the production facilities must have been common knowledge at the R&D centers.

I am only working from hearsay, as all historians inevitably must, but my take on it is Von Braun was just an ordinary man, not a monster, who found himself in a position to commandeer the resources of a government at war to further his own private dreams. In fact, he managed to do it twice. His obvious engineering and managerial talents aside, that dream and his ability to exploit the obsession of militarists and ideologues to develop the ultimate weapon was his contribution to mankind's exploration of space. If there had been no von Braun, there still would have been Nazis, but space might have been delayed for a generation.

You have to forgive Tom for his bitterness, but he wasn't just a mathematician,

he was Jewish, too.