This settles one thing
I have long felt that Second Amendment legal thinking is guided, not by any "liberal vs. conservative" division, but by "comfortable around guns vs. guns are foreign, strange, and dangerous: division. I have a number of friends and 2A advocates -- the crowning case being Mark Benenson, former president of Amnesty International's US branch -- who could be described as "liberal" by any conceivable standard.
One short segment of the "liberal" wing's dissent in McDonald v. Chicago confirms this. The dissent argues that applying the right to arms to States will make for a lot of judicial workload (as if recognizing that the First Amendment protects pornography but not obscenity did not), asks whether the right covers "Semi-automatic weapons? When is a gun semi-automatic?"
[I doubt that the dissent had in mind Webley's 1895 patent on a semiautomatic revolver, of which under 5,000 were manufactured.