But in reality the two critiques are not so similar. Many conservative politicians espouse "strict constructionalism," a judicial ideology opposed even by hard-core textualists such as Antonin Scalia as unreasonable. The more sophisticated version understands the Constitution to have a fixed semantic meaning that be derived without looking to morality or politics. But the conservative critique of liberal activism at least starts with the premise that the Constitution has a meaning that can be derived without recourse to moral or political views. Judges who allow their personal moral code or their policy preferences are diverging from the meaning of the Constitution.
Liberals tend to focus on moral concepts such as equality and liberty and expect judges to allow those concepts to illuminate the legal norms embedded in the Constitution. The academic version of the liberal view of judging (e.g., Dworkin, Tribe, etc.) also holds up the Constitution as a moral document that is interpreted based on modern sensibilities. Conservative judges who interpret the text based on semantic meaning are really setting up a facade to cover their naked political decisions because interpretation necessarily requires moral/political analysis.
So frankly I don't understand the this passage written by two pretty liberal legal scholars:
[McCain] voted to confirm every Bush nominee, and has said he will select conservative judges and would not have selected Justices Ruth Bader Ginsburg, Stephen G. Breyer, David H. Souter, or John Paul Stevens (the latter two Republican-appointed), judges widely respected for placing the law ahead of politics.
If ingredient in constitutional interpretation is the integration of moral values with legal concepts, then in what sense do the above named justices put law ahead of politics? Part of law is politics (or morality or whatever you want to call it) by their own definition. So unless we define "law" as "good liberal outcomes" and "politics" as "bad conservative outcomes" this sentence just doesn't make any sense.
At the end of the day, the liberal critique is arbitrary. If the Constitution must be interpreted morally, then why can't conservatives allow their moral views to influence their decisions? At the end of the day, the liberal critique is reducible to disputes over the most correct moral values. The conservative critique at least would, in theory, countenance liberal outcomes if that's what the semantic meaning of the Constitution mandated. So to some degree the conservative position is a bit more principled.