Of course, Andrew Sullivan is whining about how Sanford's peccadilloes require him to change his tune on gay marriage, and start supporting it instead of opposing it. That's pretty illogical, says Rod Dreher, and I concur. But it's a phenomenon I've noticed before, particularly from people who are to the left on social issues.
The argument always goes like this: If a prominent conservative (or someone near him) violates a moral law, his hypocrisy should be taken as proof that the moral law is bunkum, and ought to be dismantled; and if the prominent conservative doesn't agree than he's just showing the depth of his hypocrisy. Thus, if a Republican commits adultery he should support gay marriage; if Rush Limbaugh abuses prescription drugs he should have to support drug legalization, if Sarah Palin's daughter has a child out of wedlock then Sarah should have to support government-funded birth control, etc.
The problem with this argument is that it fails to understand what conservatives, particularly Christian ones, believe about sin--and it illustrates what social liberals and people who like to add a hissing "ists" to the end of the word Christian completely fail to grasp.
In a way, these social liberals (that is, those who are liberal on social issues) are all, no matter what religion they may practice, spiritually a bunch of frustrated Calvinists (or at least, the popular conception of a Calvinist). People are either good, or bad. If Christian, they are either saved, or damned. If saved, then they commit no sin and live lives of shining purity and virtue; if damned, they end up in Argentina with a mistress and a flimsy excuse. Since most people's behavior shows that they're clearly not saved, then there's no reason to expect any sort of morality, and certainly no reason to have any public standards of morality, such as might reasonably be expected by marriage laws or the like.
But most Christians don't view things this way. As a Catholic, for instance, I can say that the possibility of sin occurring at a regular basis even in the life of someone sincerely trying to follow Christ is one reason why the Sacrament of Reconciliation makes so much sense. Even when we're doing our best to live according to Christian principles of morality and virtue, we can and do fall. If we smugly think that there's some sin or other we would never commit--well, I think of my former pastor, who would say things like "How do you know you'd never commit adultery? Has anybody ever asked you to?"
Believing that we're somehow above sin is a kind of presumption, one that can be managed with frequent sacramental Confession, sincere examinations of conscience, and a close relationship with Christ in the Blessed Sacrament. It's not true that good Christians don't sin--the difference for a Christian is that he's supposed to try to avoid sin, and to sincerely repent of it should he fall into it.
The moral laws are not less important because Christians sin--if anything, they're more important because we do. And our civil laws become tyrannical and oppressive when they are set up in opposition to the moral law--we have only to look at abortion laws, and the way these laws have led to less freedom of speech and assembly (bubble zones around clinics) for just one example.
So, no, Sanford's hypocrisy proves only that he personally failed to live up to the moral law, not that the moral law ought to go. The fact that despite years of people failing to live up to their marriage vows we've never had some strong "pro-adultery" lobby demanding changes to marriage laws ought to illustrate that, even to Sullivan.