Comparing the Bible and the Qu'ran

According to John Loftus, critiques of other religions either simply quote the Bible as an authority, thus begging the question, or else, in their analysis of the other religions, they operate from the perspective of methodological naturalism with respect to the other religions while failing to employ that same methodological naturalism in dealing with the Christian Bible. That is why Christianity fails the outsider test for faith.

No doubt critics of Christian apologetics will take issue with some of the claims put forth in this comparison. But I don't think the case can be made that the author is employing a different standard for the Bible and for the Qu'ran. Nor does this comparison support Loftus' claim that any analysis of the Qu'ran either presupposes the inerrancy of Scripture or is methodologically naturalistic.

I would like to see some evidence to support Loftus's claims that Christians employ methodological naturalism when they critique other religions. It seems howlingly false to me.