From the wiki page concerning Von Brauns knowledge and involvement with abuse of Jewish slave laborers...
Slave labor
SS General Hans Kammler, who as an engineer had constructed several concentration camps including Auschwitz, had a reputation for brutality and had originated the idea of using concentration camp prisoners as slave laborers in the rocket program. Arthur Rudolph, chief engineer of the V-2 rocket factory at Peenemünde, endorsed this idea in April 1943 when a labor shortage developed. More people died building the V-2 rockets than were killed by it as a weapon.[34] Von Braun admitted visiting the plant at Mittelwerk on many occasions, and called conditions at the plant "repulsive," but claimed never to have witnessed any deaths or beatings, although it had become clear to him by 1944 that deaths had occurred.[35] He denied ever having visited the Mittelbau-Dora concentration camp itself, where 20,000 died from illness, beatings, hangings and intolerable working conditions.[36]
On August 15, 1944, von Braun wrote a letter to Albin Sawatzki, manager of the V-2 production, admitting that he personally picked labor slaves from the Buchenwald concentration camp, who, he admitted 25 years later in an interview, had been in a "pitiful shape".[not in citation given][1]
In Wernher von Braun: Crusader for Space, numerous statements by von Braun show he was aware of the conditions but felt completely unable to change them. A friend quotes von Braun speaking of a visit to Mittelwerk:
It is hellish. My spontaneous reaction was to talk to one of the SS guards, only to be told with unmistakable harshness that I should mind my own business, or find myself in the same striped fatigues!... I realized that any attempt of reasoning on humane grounds would be utterly futile.[37]
When asked if von Braun could have protested against the brutal treatment of the slave laborers, von Braun team member Konrad Dannenberg told The Huntsville Times, "If he had done it, in my opinion, he would have been shot on the spot."[38]
Others claim von Braun engaged in brutal treatment or approved of it. Guy Morand, a French resistance fighter who was a prisoner in Dora, testified in 1995 that after an apparent sabotage attempt:
Without even listening to my explanations, [von Braun] ordered the Meister to have me given 25 strokes...Then, judging that the strokes weren't sufficiently hard, he ordered I be flogged more vigorously...von Braun made me translate that I deserved much more, that in fact I deserved to be hanged...I would say his cruelty, of which I was personally a victim, are, I would say, an eloquent testimony to his Nazi fanaticism.[39]
Robert Cazabonne, another French prisoner, testified that von Braun stood by and watched as prisoners were hung by chains from hoists.[40] Von Braun claimed he "never saw any kind of abuse or killing" and only "heard rumors...that some prisoners had been hanged in the underground galleries".[41]