Holocaust deniers are a special reptilian species. Until the late 1980s, David Irving, a British historian focusing on World War II, was reasonably well respected among his peers, though even his best-known book, 1977’s Hitler’s War, controversially claimed that Hitler had no knowledge of the Holocaust. Later, Irving took that argument even further, denying the existence of the gas chambers and arguing—based on specious evidence—that the Holocaust never even happened.