Of course the justices aren't a jury, and their rulings concerning constitutional law don't resemble jury decisions.  I would be glad to have a lesbian on the court, for reasons similar to the ones you've cited.  But this way of thinking about the court also has its dangers, since it probably involves uncritical notions of "subject position."

Incidentally, the latest news suggests that Kagan may not be a lesbian; but whatever the case, there's apparently a whisper campaign against her -- not for the first time in recent court history.  A question that strikes me as more interesting, maybe, concerns the religious backgrounds of the justices, a matter that embroils us a little less in assumptions about subject position, identity, or experience.

The Supreme Court is not a jury, it's the top level of an independent branch of the federal government. "Peers" have nothing to do with the nomination/selection process unless the Senate and President decide they should.

While I think it's an odious point to bring up as a qualification, it is certainly a valid one from a policy perspective. And very germane to the views of the people Republicans represent (as well as the American public at large - 57% oppose gay marriage, and only 40% support it). SCOTUS nominations are all about ideology and biography/identity. As you were saying, the Supremes are going to have to rule on this in the next few years: the laws are ambiguous and piecemeal. If a politician's views trend towards support for DoMA, they will absolutely need to know whether the nominee's sexual orientation will be a factor in their decision-making process on the matter of gay marriage - it's their job.

'Bigotry' is valid: legally and politically.

Anyway, you're missing the real story: bigotry against American Protestants. With her confirmation, there will be no justice for them... They'll just have to settle for the rest of the government. And Texas: they can keep it.