The case, Arizona v. Berger, might actually be right as a matter of law--mostly because the Supreme Court has really taken the teeth out of any proportionality requirement the 8th amendment might impose. If you can sentence someone to life in prison for stealing golf clubs, or for a first time possession of cocaine rap (both cases cited by the court), then I have a hard time saying that possessing 20 pictures of child pornography is any more shocking (Douglas Berman accurately points out that this posed no barrier to examining the parallel clause in the Arizona state constitution, however). But what Keiser illustrates is that such a jurisprudence is one that's gone deeply awry. The sentence here is longer than the presumed sentence for rape, for second degree murder, or (ironically) for sexual assault against a minor. Discontinuities like that occur when criminal law views itself as in the business of expressing moral outrage. To quote Keiser at length:
The Berger case is one of the latest examples of enemy jurisprudence, of moral wrath using the legal system, and with it the government’s monopoly on the exercise of lawful violence, to destroy the lives of undesirables. The decision in Berger cannot be rationalized with arguments from traditional consequentialist or retributive theories of punishment, as it violates every requirement of proportionality....
The sentence in Berger is largely expressive conduct. It uses law as a means to display moral outrage. It is a celebration of moral hatred, as aptly described in the opening chapter of Michel Foucault's Discipline and Punish. A free society under the rule of law critically depends on the separation of the legal and the moral system. The code of the moral system is right/wrong. The code of the legal system is lawful/unlawful. By incorporating notions of morality, the law has transformed them into legal categories. That transformation of moral into legal categories is of particular significance in the context of criminal law. Moral categories tend to be absolute. Legal categories never are. In the criminal law context, the law does not only capture a society’s sense of moral condemnation, but also and more importantly for a free society, it imposes limits on what a government can do to the offender. These limits are the essential contribution of the law in the process of punishment. And in cases like Berger, these limits have all but disappeared....
The Berger case is a vivid illustration of that point. Here, the offender was technically not punished, if we require punishment to be a meaningful intra-societal answer to the offense. Rather, the boundaries of society have been redrawn so as to exclude the offender. Ejected from society into a natural state, society is free to wage war, to lash out and crush the offender, unrestrained by considerations of proportionality.
To the extent that Keiser is saying that law is not (or should not) be an instrument of morality, I disagree with him, but I don't think that's his claim. I think it's facile to claim that law and morality are, should be, or ever can be divorced. But I think that there is value in saying that law should not be used merely to express social outrage. There has to be some utility behind it. And again, this is a bigger problem when the subject is criminal law, when the legal sanction is not an injunction and a settlement, but prison or even death. In many ways I think that racial discrimination is as grave a moral wrong as mere possession of child pornography, but I don't think that it should generally come with criminal punishment (I do think that possession of child pornography is worthy of criminal sanction--but not life in prison for owning 20 images).