Doesn't matter what you think.....it matters what his peers think and they thought he was the one of the greatest rocket scientists of his generation, as did the NASA administration that employed him and the US Govt who awarded him the National Medal of Science, as well as 12 honourary doctorates, the Werner von Siemens Ring, Smithsonian Langley Medal, Order of Merit of the Federal Republic of Germany, NASA Distinguished Service Medal among others...
Yeah, Werner Von Braun was and is considered one of, if not the best Scientist in his specific field. That is undisputed.
They are great scientists because of their work, it is not necessary to also be a great person.