I think that a three-way comparison, one also bringing in Judaism, would have enabled him to make his points more strongly. Islam is, I think, a heresy of Judaism rather than Christianity, since Mohammed' s religion took on its shape a Medina as he clashed with the Jews there. The Koran is, more or less, a substitution for the Pentateuch. That said, the fideism of modern evangelicalism, with its indifference to theology, and its
arminianism are points of similarity to Islamic fundamentalism.
There has long been discussion over whether Islam was a Christian heresy or a Jewish heresy. Personally, I think Mohammed was somewhat of an equal-offender borrower from other religions, which is precisely one of the things that makes it hard for people to deal with Islam intellectually. It's slippery, parts of it bear a fleeting resemblence to some Jewish or Christian belief or text or figure, and it even has many pagan components that no doubt baffled the good pagans of their day.
You changing positions on me again? About a year ago you were blaming Christians who recognized James as their church leader for the Islam so-called "heresy".