Terry Eagleton treats this particular subject in his final lecture/chapter, but I thought it necessary to say a few words up front as to why this subject, which seems passe, is a vital issue at our particular historical moment. Before I get there, I think it important to say a few words about how my own mind has changed on a related matter.
A few years back, I spent quite a bit of time defending my own reading of the late Richard Rorty. I even subscribed, in a general way, to some of Rorty's views not just regarding language and metaphysics, but social hope as well. I have been troubled ever since with my own subscription to this point of view. Reading Eagleton has crystallized why on some matters, although I must say that Rorty's rather offhand shrug toward human suffering seems to me grotesque, particularly in light of our recent history. The best we can hope for, Rory says, is a world that sucks slightly less than it does currently. To even believe in more than that is to subscribe to a set of tenets that undermine themselves because they are rooted in an ontology that is no longer tenable. I cannot ascent to such a dim, dismal view, not just of the possibility for our human future, but to the prospects for political action rooted in a different set of assumptions.
While Rorty does have a certain insight regarding the contingency of language and thought, as well as explaining both the similarities and differences between different modes of human understanding, one need hardly buy his view whole hog to nod one's head in agreement with the view that, from a certain general methodological point of view, there isn't a whole lot of difference between the scientific investigation of a discrete physical object or phenomenon and the literary critical approach to a text. On the other hand, it makes all the difference in the world if the phenomenon being explored will be used as a tool to decimate innocent people, or the text being read offers tools for clarity regarding one's social situation.
All that by way of introduction. The God debate matters quite simply because it is part of a debate about what kind of a society we wish to be. Aside from all the other issues regarding the militant atheism of Ditchkins lies a certain complacency regarding the status quo that, to many of any or no faith is questionable indeed. This is more than just a question of politics or ideology in the broader sense. A person who insists that the very notion of some kind of divine grounding of existence is not fit for the modern world should be asking him or herself what, exactly, about our current historical moment compels anyone's assent to it. Our economies are in a shambles; our politics are in hoc to the bankers and broader corporate interests, without even the fig leaf of legal obfuscation anymore thanks to the Supreme Court; our military spans the globe, pitting the children of a stressed working class against the children of an oppressed religious system yearning for nothing more than the freedom to exist. The only "winners", at this point, would seem to be those who escape with their lives and psyches intact, a prospect made more and more dim as our military personnel are cycled again and again through combat zones.
At the heart of the Gospel message, indeed of the Biblical narrative, as Eagleton makes clear in prose that is both succinct and beautiful, is the message of Divine love and human freedom, linked in an ethical project that can be summed up by living this out together. The billions enslaved in the name of the State or capital or Dear Leader would be hard pressed to see anything triumphant in western liberal humanism beyond the threat of death; those who refuse to assent to its once-liberating but now stultifying views are consigned to a historical garbage heap by these proponents of a supposed expansive humanism, so I doubt they would willingly agree to go along, unless "willingly" includes "fearing for one's life".
The God Debate matters because, at heart, it is a debate not about God. God's existence does not depend upon our assent to a set of propositions regarding its possibility; indeed, belief (as Eagleton is at pains to point out) is not propositional at all. It is, in his usage, performative, that is, it is how one lives one's life. Hitchens utters a banal truth when he claims that religious belief has nothing interesting to say with the invention of the telescope and microscope. It is banal because the Christian faith was never about these things to begin with.
At the end of the day, Dawkins, Hitchens, Dennett, and Harris are not egregious because they have somehow insulted people of faith. Their crime - and it is, in a way, a crime - is to be far too insouciant toward the very real sufferings of so many at the hands and weapons of those who take succor at their triumphalism. One need not be a faithful Christian or Jew or Muslim to find this truly horrible.
But, it doesn't hurt, either.