...while on the left, the most bothersome recent tick has been the preemptive insistence that if conservative Supreme Court justices strike down the individual mandate in President Obama's health care bill, it'll be an expression of pure partisan allegiance rather than an earnest expression of discomfort with Commerce Clause jurisprudence as it's evolved over the decades since New Deal era case law broadened and transformed it.
While I don't condone liberals making a purely partisan argument against the Supreme Court for being purely partisan, I think the court (both liberals and conservatives) consists of partisan people. Everyone is partisan to a certain degree. Everyone grows up being told to believe in a certain partisan perspective. They either keep that perspective, reject it and accept the competing perspective, or they just don't care about either.
Obviously, if you decide to go to law school and become a judge, you care about politics in at least a very broad sense. But even if you stay outside of the more focused politics that most of the country is involved in, you are still in some manner operating under a partisan view of the world. I'm sure some political scientists have done the research. And I'm confident the data would show most SC justices hold what we would call partisan positions on nearly every issue. Even someone like Justice Kennedy can probably be labeled at least slightly partisan.
And that's fine. It's inevitable. When you think about issues and what you believe about them you tend to try and stay within a logical framework. Granted, I can probably pull some Scalia opinions out that would refute the logical framework thing. But even if you think Scalia is unfit for the bench, it's not as if he is always writing opinions no one else concurs with.
By the way, what would a non-partisan judge look like? Has anyone every described this judge when they complain about partisanship? If they can't at least make that attempt you know something is wrong with the premise of a non-partisan judge. What liberals (and conservatives) should do is ask for a good argument from these partisans. It doesn't matter if you are the most partisan person in the world if you make a good argument. Yes it's annoying that the ACA might get ruled against, and for at least partially partisan reasons. But the way to avoid that is to get Democrats elected and thus liberal judges nominated to benches.
Update: However, Scalia doesn't have to be this dumb:
ON the second day of oral arguments over the Affordable Care Act, Solicitor General Donald B. Verrilli Jr., trying to explain what sets health care apart, told the Supreme Court, “This is a market in which you may be healthy one day and you may be a very unhealthy participant in that market the next day.” Justice Antonin Scalia subsequently expressed skepticism about forcing the young to buy insurance: “When they think they have a substantial risk of incurring high medical bills, they’ll buy insurance, like the rest of us.”
If this were true we wouldn't have a problem with the uninsured. It would also mean that people have some sort of clairvoyance about when they will need insurance, which would almost refute the need for insurance altogether. This may be Scalia being too partisan. But I think the best way to refute it is to point out how poor the argument is and make a better one, not just complain that he is being a partisan.