The anecdote is taken from Eustace Mullins's The Biological Jew. Other shit of dubious authenticity like this is the "Racial Program for the 20th Century" . It's a standard practice of Jews to release the truth in an easily discreditable package as a way of providing cover for their behavior. I think you'd find Rabbi Rabinovitch to be a "shadowy, mysterious" figure—certainly more so than other rabbis, like Stephen Wise. There are certainly more credible sources about the targeting of whites.