Defiant to the end, Hitchens' letter reflects his customary style of rhetoric over substance, so there is little in terms of argument to critique.
However, his article provides insight into modern assumptions about the ultimate source of value and meaning:
It is our innate solidarity, and not some despotism of the sky, which is the source of our morality and our sense of decency.
He goes on to explicate this choice:
That essential sense of decency is outraged every day. Our theocratic enemy is in plain view. Protean in form, it extends from the overt menace of nuclear-armed mullahs to the insidious campaigns to have stultifying pseudo-science taught in American schools. But in the past few years, there have been heartening signs of a genuine and spontaneous resistance to this sinister nonsense: a resistance which repudiates the right of bullies and tyrants to make the absurd claim that they have god on their side. To have had a small part in this resistance has been the greatest honor of my lifetime: the pattern and original of all dictatorship is the surrender of reason to absolutism and the abandonment of critical, objective inquiry. The cheap name for this lethal delusion is religion, and we must learn new ways of combating it in the public sphere, just as we have learned to free ourselves of it in private.
Notice how Hitchens frames the issue; we are left to choose between oppressive concepts of objective truth ("despotism"), on the one hand, and dignity enriching subjectivism, on the other.
This is all downstream of Richard Rorty and his famous essay Objectivity or Solidarity, where Rorty defends subjectively defined community. Here are some representative excerpts (emphasis original):
There are two principle ways in which reflective human beings try, by placing their lives in a larger context, to give sense to those lives. The first is by telling the story of their contribution to a community. This community may be the actual historical one in which they live, or another actual one, distant in time or place, or a quite imaginary one, consisting of perhaps a dozen heroes or heroines selected from history or fiction or both. The second way is to describe themselves as standing in immediate relation to a nonhuman reality. This relation is immediate in the sense that it does not derive from a relation between such a reality and their tribe, or their nation, or their imagined band of comrades. I shall say that stories of the former kind exemplify the desire for solidarity, and that stories of the latter kind exemplify the desire for objectivity. Insofar as a person is seeking solidarity, she does not ask about the relation between the practices of the chosen community and something outside that community. Insofar as she seeks objectivity, she distances herself from the actual persons around her not by thinking of herself as a member of some other real or imaginary group, but rather by attaching herself to something which can be described without reference to any particular human beings.
The tradition in Western culture which centers around the notion of the search for Truth, a tradition which runs from the Greek philosophers through the Enlightenment, is the clearest example of the attempt to find a sense in one's existence by turning away from solidarity to objectivity. The idea of Truth as something to be pursued for its own sake, not because it will be good for oneself, or for one's real or imaginary community, is the central theme of this tradition.
By contrast, those who wish to reduce objectivity to solidarity--call them "pragmatists"--do not require either a metaphysics or an epistemology. They view truth as, in William James' phrase, what is good for us to believe...They see the gap between truth and justification not as something to be bridged by isolating a natural and transcultural sort of rationality which can be used to criticize certain cultures and praise others, but simply as the gap between the actual good and the possible better.
Part of the instinctive resistance to attempts by Marxists, Sartreans, Oakeshottians, Gadamerians and Foucauldians to reduce objectivity to solidarity is the fear that our traditional liberal habits and hopes will not survive the reduction...I think that putting the issue in such moral and political terms, rather than in epistemological and metaphilosophical terms, makes clearer what is at stake. For now the question is not about how to define worlds like "truth" or "rationality" or "knowledge" or "philosophy," but about what self-image our society should have of itself. The ritual invocation of the "need to avoid relativism" is most comprehensible as an expression of the need to preserve certain habits of contemporary European life.
We should say that we must, in practice, privilege our own group, even though there can be no noncircular justification for doing so. We must insist that the fact that nothing is immune from criticism does not mean that we have a duty to justify everything. We Western liberal intellectuals should accept the fact that we have to start from where we are, and that this means that there are lots of views which we simply cannot take seriously.
The best argument we partisans of solidarity have against the realistic partisans of objectivity is Nietzsche's argument that the traditional Western metaphysico-epistemological way of firming up our habits simply isn't working anymore. It isn't doing its job. It has become as transparent a device as the postulation of deities who turn out, by happy coincidence, to have chosen us as their people.1
In at least one critical sense, Rorty has won the philosophical debate, and this is reflected in Hitchens' piece.2 The secular world, through the influence of the university, accepts these terms: either we choose unity through subjectively defined, community-based morality, or we suffer under those who think they have a divine mandate that allows them to bend the world to their will.3
Even though Hitchens' dilemma is ultimately false (and deeply problematic, for it ends in claiming God as the fundamental problem with the world!), it is partially correct. Formed in the image of a Triune God, we only thrive in loving, service-oriented community. History is filled with examples of professing believers brutalizing those outside of their community. We may only need mention the Catholic Church of the middle ages and its cultural expectations of "how things ought to be"; claiming that its cultural values were derived from a transcendent standard, it laid a delightful foundation for every sort of rank imperialism and colonialism. And Scripture gives us several case studies of claimed followers of God exercising injustice against those who do not hold to the in-group's standard of righteousness. (A prime example is that of the Pharisees.) The thirst for solidarity is natural and good, and there is a limited, qualified sense in which objectivity ruins its pursuit.
Yet because Scripture accounts for this behavior--the misuse of God's truth for selfish, destructive ends--such activity cannot be a sufficient objection to theism.
Indeed, Scripture offers a positive alternative. Christ has come to establish a kind of community that promotes not just in-group solidarity, but love for those outside of the group, even if they are enemies.4 In one sense, the Sermon on the Mount presents a choice between two kinds of objectivity: (a) one which inevitably brings derision, scorn, hate, and even violence, toward those who are not part of the in-group, and (b) another which brings peaceful, loving, tolerant solidarity to both those inside and outside the group. In the former, exemplified by the Scribes and the Pharisees, you earn your social and religious standing through righteous obedience to an extrinsic standard. This acceptance inevitably produces a superiority complex out of which arrogance and oppression flow. In the latter, however, acceptance into Christ's kingdom is grace from beginning to end, a justification by faith alone. Since you do not earn the love of God, there is no ground on which to say you are better than those in the out-group. Since you understand your own sinfulness, and what Christ sacrificed to save you from it, you will have grace and power to love others, even those who hate and despise you.
The love of Christ shatters the post-modern dilemma. In Jesus you will find both objective meaning and loving solidarity.
1. Richard Rorty, Objectivity, Relativism and Truth (Cambridge: Cambridge University Press, 1991), 21ff.
2. Strangely enough, here we also find the basis of Brian McLaren's objections to modern Christianity, whether in its conservative or liberal forms.
3. While Rorty's essay targets all forms of objectivity, including scientism, Hitchens' narrowing of the scope of objectivity to theism is reasonable given his intended audience of American atheists.
4. I am indebted here to Timothy Keller's conception of Christ's community as described in "The Community of Jesus." This sermon, an exposition of Luke 6:12-36, is available for free, either on the Redeemer podcast or here at the Redeemer website.