The following is an excerpt from the Wikipedia entry “Veritatis Splendor” with only the pertinent hyperlinks retained.
Veritatis Splendor (Latin for "The Splendor of Truth") is an encyclical by Pope John Paul II. It expresses the position of the Catholic Church regarding fundamentals of the Church's role in moral teaching. The encyclical is one of the most comprehensive and philosophical teachings of moral theology in the Catholic tradition. It was promulgated on August 6, 1993.
Veritatis Splendor responds to questions of moral theology that had been raised in the Church, especially in the latter half of the 20th century. These questions revolve around man's ability to discern good, the existence of evil, the role of human freedom and human conscience, mortal sin, and the authority of the Magisterium of the Catholic Church in guiding man. In response to these, Pope John Paul II emphatically insists that moral truth is knowable, that the choice of good or evil has a profound effect on one's relationship with God, and that there is no true contradiction between freedom and following the good.
Response to moral relativism
Veritatis Splendor begins by asserting that there are indeed absolute truths accessible to all persons. Contrary to the philosophy of moral relativism, the encyclical insists that moral law is universal across people in varying cultures, and is in fact rooted in the human condition. Pope John Paul teaches that no matter how separated someone is from God, "in the depths of his heart there always remains a yearning for absolute truth and a thirst to attain full knowledge of it." He goes on to say that the splendor of truth "shines forth deep within the human spirit.
Moral authority of the Catholic Church
Ultimately, John Paul teaches, "to ask about the good, in fact, ultimately means to turn towards God, the fullness of goodness." Against the idea that the Church's teaching body has a mainly exhortatory role, the pope reiterates the Catholic doctrine that the Magisterium of the Catholic Church has authority to definitively pronounce on moral questions. Even more, John Paul teaches that the Church is Christ's particular response to help answer everyone's question of what is right and wrong.
Counting the above excerpt as a good summary of the teaching of Veritatis Splendor and its detailed refutation of moral relativism, it is clear that writers particularly must enunciate and defend those same moral precepts as the Church’s in order to avoid the label “moral relativist.”
One need not be a Catholic to do so, although Catholics—more than anybody else—ought to be the least confused about this subject, given the clear and constant teaching of their Church. However I believe it can be shown that until the early part of the twentieth century, virtually all Christians held unanimously to the same moral code as that of the Roman Catholic Church.
Which was very much an important point of my previous posting.
More resources on moral relativism:
Clever Google video on AbsoluteTruth