We face reductionisms of the Faith all the time as Catholics: liturgical expedient minimalism is one of the most noteworthy examples, then there's the identifiable dictatorship of relativism and the denial that Scripture is divinely inspired (cf. Benedict's address last week to the PBC). While not formal matters of heresy (technically defined) but they are reductions that are a gradual chipping away of the content and expression. Poor liturgical practice, banal sacred music and unprepared liturgical preaching will erode the content of faith. There are other examples but I think these three give good a sense of a problem.
I believe that Tarcisio Bertone and Joseph Ratzinger are correct: we believe, as Catholics, in revealed truth; that the faith is not debatable and we can't reduce our faith to formally defined dogmas. And while the infallibility of the papal office is restricted to a clearly defined process so as not to allow arbitrariness, the exercise of infallibility has been exercised twice since 1870. BUT there are the secondary object of infallibility that have to be acknowledged and assented to, despite what Fathers Hans Kung, Roger Haight, Randy Sachs, John Coleman and Charles Curran say.
Here's John Allen's article: A long-simmering tension over creeping infallibility by John Allen.pdf