Why are Supreme Court appointments so contentious?

The sad state of our debates on judicial appointments is a direct consequence of the strategy by liberals to enact their agenda through the courts. I can't improve on what Justice Scalia said about it in his dissent in Casey (1992, excerpt):
 
What makes all this relevant to the bothersome application of "political pressure" against the Court are the twin facts that the American people love democracy and the American people are not fools. As long as this Court thought (and the people thought) that we Justices were doing essentially lawyers' work up here - reading text and discerning our society's traditional understanding of that text - the public pretty much left us alone. Texts and traditions are facts to study, not convictions to demonstrate about. But if in reality, our process of constitutional adjudication consists primarily of making value judgments; if we can ignore a long and clear tradition clarifying an ambiguous text, as we did, for example, five days ago in declaring unconstitutional invocations and benedictions at public high school graduation ceremonies, Lee v. Weisman, 505 U.S. 577 (1992); if, as I say, our pronouncement of constitutional law rests primarily on value [505 U.S. 833, 1001]   judgments, then a free and intelligent people's attitude towards us can be expected to be (ought to be) quite different. The people know that their value judgments are quite as good as those taught in any law school - maybe better. If, indeed, the "liberties" protected by the Constitution are, as the Court says, undefined and unbounded, then the people should demonstrate, to protest that we do not implement their values instead of ours. Not only that, but the confirmation hearings for new Justices should deteriorate into question-and-answer sessions in which Senators go through a list of their constituents' most favored and most disfavored alleged constitutional rights, and seek the nominee's commitment to support or oppose them. Value judgments, after all, should be voted on, not dictated; and if our Constitution has somehow accidentally committed them to the Supreme Court, at least we can have a sort of plebiscite each time a new nominee to that body is put forward. JUSTICE BLACKMUN not only regards this prospect with equanimity, he solicits it.