You make a good point and one of the reasons that the law is silent is that, IMO, such situations have been rare, if not non existant despite claims that it happens tens of thousands of times a day.
Rather than the travesty that Krauthammer suggests, I think that the Congress took a necessary first step to protect life when such a conflict arises.
The states SHOULD do this themselves, but that doesn't mean that Congress was wrong to pick up the ball when Florida dropped it.
The travesty, if there is one, is that Congress took so long to take this issue up. By waiting, Terri is now 5 days closer to death than she should be.
The problem is not marriage, I know plenty of folks who are committed for life. The problem really isn't the courts. Contrary to what many might believe, most are constrained by the limits of the law. The problem is with us. Laws were not in place to help folks like Terri. Meanwhile, conservatives keep looking to the feds and Congress for help. That's absurd. State legislatures are best suited to address the problem. They need to be deluged with people demanding that the laws concerning guardianship and end of life decision-making be reworked.