He is right that Christians can find glimmers of truth in other religions, but this is only useful in seeing how Christ is the fulfillment of all that was good and true in all pre-Christian religions, not just Judaism. (C.S. Lewis called pagan ideas of dying-and-rising gods 'good dreams', the Buddha rightly rejected many pagan notions and rightly stressed dispassion, many of Lao Tsu's descriptions of the Tao fit Christ with a fidelity equal to Isaiah's suffering servant passages, and so forth.)
Islam, however, represents a decline from the Gosple, a denial of God's self-revelation and an insistence on His imprisonment in a humanly conceived transcence, a prison from which He can reveal only His will and not Himself. It represents, too, a decline from the 'high anthropology' of Genesis. "Allah has no image," is stronger than an injunction against idolatry: it denies "Come let Us make Man in Our image and likeness," and in so doing provides the basis for the perpetuation of slavery and the devaluation of human life to the point that young people with their lives full before them are devalued into guidance systems for bombs.