Cardinal Ratzinger's sermon on relativism at the Mass for the Election of a Supreme Pontiff hit the note most important both in his own life and in the coming life of the Church, in an age calling itself "post-modern" but perhaps more accurately described as the Age of Meaninglessness.
In his most formative years, Ratzinger heard Nazi propaganda shouting that there is no truth, no justice, there is only the will of the people (enunciated by its leader). As its necessary precondition, Nazism depended on the debunking of objective truth and objective morality. Truth had to be derided as irrelevant, and naked will had to be exalted.
To anybody who said: "But that's false!" the Nazi shouted, "That's just your opinion, and who are you, compared to Der Fuehrer?"
To anybody who said, "But what you are doing is unjust!" the Nazi shouted louder, "Says you, swine."
Relativism means this: Power trumps.
Ratzinger experienced another set of loud shouters in the 1968 student revolution at Tubingen University, this time in the name of Marxist rather than Nazi will. Marxism as much as Nazism (though in a different way) depended on the relativization of all previous notions of ethics and morality and truth -- "bourgeois" ideas, these were called. People who were called upon by the party to kill in the party's name had to develop a relativist's conscience.
In today's liberal democracies, Ratzinger has observed, the move to atheism is not, as it was in the 19th century, a move toward the objective world of the scientific rationalist. That was the "modern" way, and it is now being rejected, in favor of a new "post-modern" way. The new way is not toward objectivity, but toward subjectivism; not toward truth as its criterion, but toward power. This, Ratzinger fears, is a move back toward the justification of murder in the name of "tolerance" and subjective choice.
Along with that move, he has observed (haven't we all?), comes a dictatorial impulse, to treat anyone who has a different view as "intolerant." For instance, those (on the "religious right") who hold that thereare truths worth dying for, and objective goods to be pursued and objective evils to be avoided, are now held to be "intolerant" fundamentalists, guilty of "discrimination."
In other words, the new dictatorial impulse declares that the only view permissible among reasonable people is the view that all subjective choices are equally valid. It declares, further, that anyone who claims that there are objective truths and objective goods and evils is "intolerant." Such persons are to be expelled from the community, or at a minimum re-educated. That is to say, all Catholics and others like them must be converted to relativism or else sent into cultural re-training camps.
On the basis of relativism, however, no culture can long defend itself or justify its own values. If everything is relative, even tolerance is only a subjective choice, not an objective mandatory value. Ironically, though, what post-moderns call "tolerance" is actually radically intolerant of any view contrary to its own.
Most of the commentators, however, even those who support him, are misinterpreting Ratzinger's point. They are getting him wrong.