Apparently Rowling discovered, after having already invented the racist ideals of the Death Eaters on her own, just how close the real world ideology of the Nazis really was. She visited a Holocaust memorial and discovered the lengths the Nazis went to to determine someone’s supposed racial purity.
Wow. To have done a lot of research is admirable. To have independently come up with so many parallels is… icky. My condolences to Ms. Rowling, that must have been a shock to her.