The entire point of Fitzgerald's researches into the language of scholarship is to point out that scholars who use the word "religion" are not stating an objective fact but making an argument, you know, kind of like Israelis using the word "terrorist" to describe Hamas, or Hamas using the word "racist" to describe Israel. It's a point that needs very much to be made in the world of international relations. Some IR areas, like China studies, do not use the word "religion", because it doesn't help their arguments often. Unconsciously, they look at Chinese culture and realize that "religion" is a divisive word that doesn't accurately categorize similar kinds of organizations. Others, like Middle East studies, use "religion" frequently, uncritically, and without challenge. It's sloppy methodology that exposes various kinds of bias.
So why is Fitzgerald's criticism growing overtly dualist himself? He does not seem to have taken seriously the criticism of his earlier The Ideology of Religious Studies by Frank J. Korom in Religious Studies Review 27.2 (2001). Korom pointed out, essentially, everyone has their own personal bias, and the word "religion" can be employed for many different possible goals, not just the imperialist West against the subaltern East. Rather than responding to that argument, in this book the vague "ecumenicism" of Ideology has grown into a hideous monster called "secular liberal capitalism", "capitalist corporate interests", "the secular scientific rational", etc. I do not doubt that most politicians want to preserve the "secular politics" that defines their power against the segregated power of "religion". But what the category of the secular means to the people who employ that word is not determined by an evil monster.
Fitzgerald inadvertently PROVES this by citing a Hindutva author, Atal Behari Vajpayee, who wishes to construct a new secularism for India based on the views of the BJP. Vajpayee is an excellent example of a bold category of thinkers who reject outside attempts to define their status quo through intelligent use of language itself (although, obviously, he is not the master of Indian English and others may disagree with him). Is Vajpayee part of "secular liberal capitalism" because he calls the BJP secular? I do not think this bogeyman exists. Nobody has a monopoly on the word "secular". You can insert the word in your essay, thesis, or poem at any time, and tell the world that what others call a religious matter is truly secular, or vice versa. The definition will be decided by whether intellectuals treat arguments like yours with respect, and with resulting policy decisions and court cases, and occasionally with resulting atomic bombs. That arguments like this can be made by anyone at any time, and are quite serious and not fuel for mockery, is what IR scholars need to understand.
Fitzgerald makes the same mistake in his conclusion when he refers to "an imagined false religion Hinduism". This phrase is perhaps true in the limited context of Max Muller's ecumenical project, but the eager adoption of that word by millions of Indians suggests that Hinduism is not an ongoing falsehood. Rather, it is a word, like "Christianity", "religion", or "globalism", that contains an argument. In fact, it contains many fun arguments, such as whether atheists are Hindus, and whether Buddhists are Hindus. People are going to continue to use these words, because they are powerful. Scholars would do better to be more careful with their language, but these arguments do appear nonetheless. Fitzgerald argues in this book that these categories are "myths", unnoticed generalizations that unite diverse people against other diverse people. But maybe "myth" is a divisive word; after all, it was first used in English in 1830, shortly after the word "Hinduism", as a neologism to describe "other people's stories".
This book has an idea that international relations scholars need to pick up on. Unfortunately, I will have to recommend it with caveats, because while it does have its high points, it also loses track of its most important ideas at times.