He is referring to Isaac and Ishmael with Islam being born of from Ishmael and Judaism being from the Isaac side of the family.
I dont see how thats works
He was saying that Islam should not be necessarily be treated differently from other religions, because the danger is what lies with even what a harmless version of religion can breed. Its effects may seem dormant, they are still latent.
He argues Islam was born out of a singular event in history, the backlash on secular hedonistic Jews and Hannakah.
I've done a little rooting around, I think this is where he is coming from..
Enter Hanukkah. Created, Hitchens argues, as a way to pit the secular populism of the Maccabees (good) against the imperialistic and decadent tendencies of Hellenism (bad), Hanukkah was designed to stop the slide into secular hedonism. It's Hanukkah as propaganda, selling straying Jews on the miracle of the burning lamp before they stopped believing entirely. From there, Mr. Hitchens writes, all competing visions of hell broke loose:
"The Hasmonean regime that resulted from the Maccabean revolt soon became exorbitantly corrupt, vicious, and divided, and encouraged the Roman annexation of Judea.
Had it not been for this no-less imperial event, we would never have had to hear of Jesus of Nazareth or his sect-which was a plagiarism from fundamentalist Judaism-and the Jewish people would never have been accused of being deicidal 'Christ killers'
"Thus, to celebrate Hanukkah is to celebrate not just the triumph of tribal Jewish backwardness but also the accidental birth of Judaism's bastard child in the shape of Christianity. You might think that masochism could do no more. Except that it always can.
Without the precedents of Orthodox Judaism and Roman Christianity, on which it is based and from which it is borrowed, there would be no Islam, either".
http://www.jewcy.com/tags/christopher_hitchens So there you have it folks. Islam was born out of Hannakah