Answer

The source of the quote was, as Dave correctly answered, Josef Ratzinger. The immediate source of the quote is his recent book Truth and Tolerance, though it appears in an essay he wrote for a festschrift for Karl Rahner in 1964 (in which he was guardedly critical of Rahner's "anonymous Christian" thesis). There has been some speculation about Pope Benedict backtracking on his more adventuresome ideas after the unrest of 1968. whatever the merits of that reading of his life, the fact that he made the decision to include this essay in a book published in 2003 actually says a great deal about the consistency--and daring--of his own theological thought.

The quote again: "In its theology of the history of religions, Christianity does not simply take the side of the religious person, take the side of the conservative who keeps to the rules of play in his inherited institution; the Christian rejection of the gods signifies much rather a choice to be on the side of the rebel, who for the sake of his conscience dares to break free from what is accustomed: this revolutionary trait in Christianity has perhaps far too long been hidden beneath various conservative models."

As for being 'pretty impeccable', I submit that this wording is very unique...