He cites a variety of reasons and sources, including genetic research. That brings to mind an incident in which a peer-reviewed genetic science journal published a study indicating Israeli Jews were very close genetically to the Arabs living in the surrounding area. Due to pressure (imagine that!), the journal sent out a mailing to every recipient of the issue with the offending article. The mailing indicated the article had been revoked (disavowed by the journal's editorial staff), and included a new article. It also contained instructions on how to razor out the old article, and tape in the new. The primary subscribers to this journal are, of course, colleges, scientific institutions and libraries.
He also brings up the other written words of the author of The 13th Tribe, Arthur Koestler. He said he felt this book would lessen anti-semitism (opposition to brutal, dictatorial rule of the entire world by Jews).
My personal opinion, regardless of how it sounds on the face of it, is that the people we call "Jews" are an admixture of human beings with some sort of supernatural beings, and not the good kind. Face to face interaction with supernatural beings was an everyday part of life in Biblical times, as well as in ancient human societies all over the world. And, unlike Joseph Campbell, I don't believe that all humans, at some point, had a form of schizophrenia that caused them to hallucinate all these interactions, and / or mistake normal humans for supernatural beings.
Also, consider that Noah was described as "perfect in his generations", and that God destroyed the entire world, saving only him and his family. And references in the Bible to humans seeking to have sex with angels, "strange flesh", and I think that at least some of the references in the Bible to "strangers" indicate supernatural beings. And of course the sections of Genesis indicating supernatural beings bred with human women.
There are (allegedly) only 15 million Jews in the entire world (the population of Lagos, Nigeria), and yet they seem to rule over most of it. The Rothschild family has enough money to pay half the world to kill the other half. There are laws in most of the first world against even criticizing or questioning Jews, or having and promoting beliefs they don't like. I don't think all the hard work and intelligence in the world could land them such power, unless all that was devoted to underhanded means. And even with that, I don't think they could have managed this without some supernatural help. Consider that Christian and Islamic mysticism is barely known by the public, but Jewish mysticism (Cabala) is so well-known that celebrities take up it's study to boost their standing.