Let me try to explain why I disagree by means of an analogy. (I’m counting on readers not to infer from the fact that I’m going to compare sexual orientation to a disability for the purposes of this argument, that I regard it as a disability—I don’t!)“Well, you provide some decent *prudential* arguments for her revealing this info, and I think it's not unreasonable (though not a slam-dunk) to say that the public has a material *interest* in finding out, but I don't see how you get from there to the idea that the public has a *right* to know. The public interest may justify a senator's asking the question, but I don't see how she's under any obligation to answer.
“Of course the Senate is then free to reject her nomination because of her silence, but given that they routinely approve nominees who refuse to answer *much* more germane questions about their likely future decisions, it's hard to see why this would be a showstopper.”
Imagine a guy with bipolar disorder who manages his disability so well that no one but his psychiatrist and his immediate family knows about it. Understandably, he’d prefer to keep it that way, not only because he values his privacy, but because it wouldn’t do his successful plumbing business any good for his psychological condition to be widely known. All of us, I think, will grant that he has a right to keep his psychiatric diagnosis to himself.
Suppose that his business is doing so well that he wants to expand it. To raise the necessary capital, he decides to mount a public offering of common stock in his plumbing company with the intention of remaining its Chief Executive and Operating Officer. Under the law of fraud, because his psychiatric condition is material to the decision about whether to buy stock in his company (bipolar people do go off their meds, after all), he has waived his right to remain silent about it in his offering statement. That doesn’t mean that he never had a right to keep his psychological condition to himself—but he waived it by putting himself in a position voluntarily in which, as a matter of law and morality, remaining silent about his psychiatric condition would amount to fraud.
I don’t think that it’s much of a stretch to say that, by accepting Obama’s nomination to the Supreme Court, Kagan has made a public offering of herself. Indeed, it sounds like she has been doing her best since high school to make her life into material for an effective offering statement. If her sexual orientation is material to a citizen’s decision about whether to support her nomination--and KenB says it’s “not unreasonable” to think that it is--she has incurred an affirmative duty to disclose it and we have a corresponding right know about it. Prudence has nothing to do with it.