"In my opinion, Allah is not God of Abraham, Isaac and Jacob which means Muslims have no spiritual relationship whatsoever with Jews or Christians."
Well, we certainly can point to that moon god or goddess, I forget which, from which Allah seems derived, but the fact is that the Mahammedans say that Allah is the same god worshipped by Abraham, Moses etc. They've claimed that from the beginning. And you must admit that the complete ineffability of Allah is similar to that of God in the OT. Beyond that, the apparent vicious capriciousness of Allah fits rather well with at least some OT versions of God as well as what some Protestants profess to believe He is like. We've had a discussion on another thread here on FR about the differing views about God as between Orthodox and Latins on one side and Calvinist type Christians on the other. I myself remarked that the divergence is so profound that it is as if we worship two different "Gods".
Certainly Orthodoxy and to a lesser extent The Latin Church have similarities to and connections with Judaism. Jewish friends and a Rabbi I know marvel at the Divine Liturgy, with the Rabbi commenting that but for soem of the prayers, he imagines himself at a Temple ceremony. The Protestant connection to the OT and its ideas about the covenant God made with the Jews is self-evident. I doubt the author of this piece would deny that. Judaism exists complete within itself. That is to say, no one can call Judaism a heresy. One can say, however, that heresies arose out of Judaism just as they arose out of catholic Christianity or out of a mixture of both or the heresies of both. Islam is one such heresy and it has certain hallmarks which Protestantism shares. But as I said, I don't believe Protestantism arose out of Islam.
Well, Jesus called the rabbinic judaism of his day, with its notion that talmud took precdence over torah, a heretical national misadventure. "If you truly were true to Moses, you would love Me," Our Lord said (I paraphrase from John 8). With its additional books, and denial of the Trinity, and rejection of Jesus, talmudic judaism resembles other anti-Christian cults.