'For me, punishing a crime with another crime, which is what killing for vindication is, would mean that we are still at the point of demanding an eye for an eye, a tooth for a toothAs you read that quote, it's important to maintain the correct perspective. Catholic belief (as propagated by Pope Ratzinger) holds that Catholic Christianity is the only successful blend of "Jewish" obedience to God (faith) with Greek philosophy (reason). This marriage of faith and reason, body and spirit, is what Benedict, following a long Christian tradition, calls the "logos," the "word of God." ToThe church opposes the death penalty because it is seen to incline too far away from "Greek" reason and toward "Jewish" faith.
When the Pope's deputy says that killing for vindication is "eye-for-an-eye" morality, he is criticizing Judaism, while simultaneously misunderstanding our scripture. For at least 2500 years, Jews have understood the verse figurativly yet this Cardinal is still using it as a cudgel with which to attack Jews for being hopelessly beholden to the outdated and unreasonable Old Testament.