Hitchens argues that "religion poisons everything" by demonstrating through numerous examples that the necessary stubbornness of faith obstructs that particular flavor of reason so essential to scientific progress, parliamentary democracy, and the defense and maintenance of the humanitarian values of the modern world. Although he never uses the word, the real culprit here is dogma: faith unavailable for revision under any circumstances. With a distinction between faith and dogma, we may be able to further bolster Hitchens' position. For, though Hitchens' critique is compelling in both its passion and its reason, his positive account of an areligious human society nevertheless rest upon two crucial articles of faith. In order to provide defense against his own arguments in a noncircular (and nondogmatic) fashion, Hitchens must emphasize that the foundational articles of faith in a humanistic society are not dogmatically held, and thus [can? - will?] not poison in the sense that religion "poisons."
The first article of faith upon which a humanistic society rests is faith in science. While all modern men share a deep sense that science makes progress, that science gets at the truth, that the experimental method is an effective sacrament against superstition and ensures access to the real, it turns out to be surprisingly difficult to characterize the exact difference between such hard-won scientific "knowledge" and the divinely inspired "knowledge" of the religious zealot. In particular, Hume's discussion of the problem of induction demonstrates that there is a kernel of blind faith at the heart of the scientific endeavor (faith that the past will correspond to the future (in matters of causality, or physical law, say), a kernel which cannot be justified or defended in any noncircular manner. [This problem bleeds beyond science, for even the most basic rules of logic (modus ponens, say, or conjunction elimination, even) cannot be adequately characterized in the object language without their use in the metalanguage ~ a practice which avoids charges of circularity only through the artificial stratification of languages (but which remains conceptually circular in a profound sense).] Perhaps we can describe this kernel of faith as an undogmatic kernel ~ if the future should ever cease to be like the past, then we will revise our (mere) faith in the scientific method (and inductive reasoning in general). Not that any of the modern atheists do demonstrate such a pragmatic take on science (or that this weakened position is even easily statable in these post-Kuhnian days), yet Hitchens seems closest to such a level-headed approach, a crusader (we can at least imagine as) unafraid to weaken his position from dogma to the end of leveling a better attack against his foe.
Unfortunately, the second article of faith upon which Hitchens' humanism rests is not so easy to dismiss. In fact, it may amount to several distinct dogmas, the abandonment of any of which could scuttle Hitchens' entire argument. The problem at issue is the very source of the humanistic values which Hitchens defends and which are quintessential to Hitchens' argument against religion. For it is precisely the anecdotal violation of these values to which Hitchens repeatedly appeals as evidence that religion is "poison." Unless these humanistic values have some independent justification, Hitchens' appeal amounts to little more than rhetoric, a swaying of the audience's emotions rather than reason. How to defend these values? Hitchens seems not to realize that a defense is needed, or that there could be any question about their content. In various passages, however, he does seem to trace their source ultimately to natural rights, reason, and conscience. In particular, we may state the underlying Hitchensian many-dogmas-in-one as (something like) there is a single consistent ethical system characterized by natural rights, supported by reason, and revealed in the conscience of every modern man, and furthermore it corresponds to the system of modern humanism. Such a brash formulation may well be a mere straw man facsimile of Hitchens' actual view, but it is hard to make sense of his arguments without some such principle. Yet once it is stated in black and white, it is easily apprehended as a very fragile principle indeed. The notion of natural rights is simply too weak and circular to do the job the modern humanist demands of it; reason cannot provide an adequate basis for any normative theory (as Sidgwick so elegantly demonstrated in Methods of Ethics - to say nothing of the problems inherent in providing a noncircular characterization of reason in the first place); and the thesis that a conscience unmolded by prior ethical education (a mere manifestation of tradition) would develop humanistic values is entirely vacuous and unsupported.
However, these two problems are impediments to any modern liberal theory of society. One does not condemn Hitchens for his failure to adequately address these stumbling blocks, rather one applauds him for providing such a convincing argument that the only identifiable flaws are those which even the greatest minds before him have failed to avoid.