Think of it this way: we have a mini-trend of naming Catholics to the Supreme Court. We aren't talking about an outbreak of Catholic devotion; or the Catechism of the Catholic Church suddenly rocking the charts at Amazon.
Not that there'd be anything wrong with that.
I suggest that we are not seeing "Catholic" as a new litmus test for the Court, rather what we are seeing is a trend in which Catholic formation seems to show up when the current culture goes looking for good judgment about our common life.
Members of the Court do not write the law, but they engage with its most fundamental questions as they talk through the hard cases. How shall we decide when contracts, made in good faith, lead to conflicting results? How shall we protect minority voices in a democracy, and what are the limits of that protection? What is appropriate punishment, and which acts, in our own day, should be called "crimes"?
"Catholic issues" do not come before the Supreme Court, though religious issues do, to the extent that they arise as we interact with one another. And, at the moment, there's an interesting trend in which people with Catholic backgrounds are found to have the requisite combination of intellect, analysis and judgement -- not to mention a social sensibility (which we dare not call "empathy').
Hmmm. Appleby does seem to be making an anti-Catholic argument, "Nativist," as Gibson suggests.
I wonder if we need to look a little deeper, what if we turned her argument around...
Perhaps she's playing one card to reveal another: her real target, I suggest, is not the "Romish" tendencies of American Catholics, but rather the tendency of some Roman Catholic bishops to chastize public officials whose exercise of office seems to disregard their own authority.
In other words, it's not the Catholics on the Supreme Court that need to "recuse" themselves.