The absence of the word "Muslim" is both conspicuous and unexpected. The author used "Arab" as if talking about Muslims, but of course he should know that it is in no way a synonym. There are Arab Muslimsand even Arab atheists. About 7- 10% of Arabs are Christians. And there are non-Arab Muslims: in fact 80 percent of the world's Muslim population are non-Arab.
So that makes me wonder why his language is so imprecise. From an "expert" it seems inexplicable.