How would an American bigot have responded to an encounter with the horrors humanity is capable of due to intolerance?

Statistically speaking, I'd consider it likely some members of what I guess you'd call the "hate movement" would have had something to say about how their beliefs were/were not affected by digging up mass graves or entering a death camp. As I can find nothing about such encounters, surely another student of history may have stumbled on relevant info when reading about World War II and the holocaust?