You do not need the Constitution to reflect the wishes of the current society. Certainly the Constitution does not require discrimination on the basis of sex. The only issue is whether it prohibits it. It doesn't. Nobody ever thought that that's what it meant. Nobody ever voted for that. If the current society wants to outlaw discrimination by sex, hey we have things called legislatures, and they enact things called laws. You don't need a constitution to keep things up-to-date. All you need is a legislature and a ballot box. You don't like the death penalty anymore, that's fine. You want a right to abortion? There's nothing in the Constitution about that. But that doesn't mean you cannot prohibit it. Persuade your fellow citizens it's a good idea and pass a law. That's what democracy is all about. It's not about nine superannuated judges who have been there too long, imposing these demands on society.Other commenters have already argued that Justice Scalia's answer to the question is historically questionable or that his attitudes towards proactive lawmaking by the judiciary are selective or even self-contradictory, so we need not discuss that. However, Scalia's statement does raise one further question, which is whether law derived through jurisprudence is automatically undesirable.
I would argue that this is not the case. Certainly from a democratic standpoint, we would all like to see as much law as possible enacted through elected legislative bodies. But Justice Scalia's complaint is about law designed to protect the minority. Although we would hope that our elected representatives will be as enlightened as humanly possible, the phrase "tyranny of the majority" exists for a reason.
Although we all hope - and, one believes, history demonstrates - that legislative bodies will in the long run recognize minority rights, the simple truth is that virtually across the board minority rights have first been achieved through the courts. Brown v. Board of Education and similar decisions preceded civil rights legislation in the United States. R. v. Morgentaler preceded new abortion law in Canada. Halpern v. Canada, and then the Supreme Court's reference on same-sex marriage, preceded the legalization of same-sex marriage here, and one hopes that Perry v. Schwarzenegger will similarly precede the legalization of same-sex marriage in America.
Common-law systems rely on the judiciary to do what the masses often cannot: namely, to consider the needs and wants of minorities whose rights have been imperiled or curtailed, and find if our law is wanting. This is not a perfect system, of course, but without the judiciary's ability to create, in essence, new discrimination law, the net result would be more suffering as individual rights would be trampled upon for a longer period of time. (Possibly a much longer time, if you accept the argument that highly-publicized judicial decisions of this sort can drive public acceptance for the minority right in question.)
Justice Scalia evidently believes that democratic principles trump minority rights, and this is a fair belief to have. But it is not by any means a given.