The difference is that the non-Catholics in this case do not reflect truth. The atheist was reflecting false objections in the field of theodicy (the part of philosophy dealing with the existence of God), yet that's the specific point you endorsed. The heretic was denying an unambiguously defined doctrine of the Church (after it was defined), yet you brought him in as if he was an authority on that very doctrine.
Just so others will see what you are talking about I shall put my quote in context:
The courtship between Catholic faith and modern science reached a lower point on November 22, 1951 when Pope Pius XII once again addressed the Pontifical Academy of Sciences. The title of the Pope’s address was ‘The Proofs for the Existence of God in the Light of Modern Natural Science.’ What followed was an inferred endorsement of nearly every evolutionary theory on offer at the time, theories that (1) conflicted with the literal order of creation and the geocentric order of the universe held by the all the Church Fathers; (2) theories that denied the biblical age of 6-7,000 years for the universe; (3) theories that denied the global Flood as recorded in Genesis and its effect on the topography as we find it today, and God knows what else. Here is some of Pope’s speech:
‘44. It is undeniable that when a mind enlightened and enriched with modern scientific knowledge weighs this problem calmly, it feels drawn to break through the circle of completely independent or autochthonous matter, whether uncreated or self-created, and to ascend to a creating Spirit. With the same clear and critical look with which it examines and passes judgment on facts, it perceives and recognizes the work of creative omnipotence, whose power, set in motion by the mighty “Fiat” pronounced billions of years ago by the Creating Spirit, spread out over the universe, calling into existence with a gesture of generous love matter bursting with energy. In fact, it would seem that present-day science, with one sweeping step back across millions of centuries, has succeeded in bearing witness to that primordial “Fiat lux” uttered at the moment when, along with matter, there burst forth from nothing a sea of light and radiation, while the particles of chemical elements split and formed into millions of galaxies.’
48. On the other hand, how different and much more faithful a reflection of limitless visions is the language of an outstanding modern scientist, Sir Edmund Whittaker, member of the Pontifical Academy of Science, when he speaks of the above-mentioned inquiries into the age of the world: “These different calculations point to the conclusion that there was a time, some nine or ten billion years ago, prior to which the cosmos, if it existed, existed in a form totally different from anything we know, and this form constitutes the very last limit of science. We refer to it perhaps not improperly as creation. It provides a unifying background, suggested by geological evidence, for that explanation of the world according to which every organism existing on the Earth had a beginning in time. Were this conclusion to be confirmed by future research, it might well be considered as the most outstanding discovery of our times, since it represents a fundamental change in the scientific conception of the universe, similar to the one brought about four centuries ago by Copernicus.”50. It has, besides, followed the course and the direction of cosmic developments, and, just as it was able to get a glimpse of the term toward which these developments were inexorably leading, so also has it pointed to their beginning in time some five billion years ago. Thus, with that concreteness which is characteristic of physical proofs, it has confirmed the contingency of the universe and also the well-founded deduction as to the epoch when the cosmos came forth from the hands of the Creator.’
Yes, admits Pope Pius XII, it all began with Copernicus. Not for the first time a pope has placed the creation act and order into the hands of secular theory. But there are philosophical and theological consequences to placing the creative act of God at the mercy of science’s Big Bang and the condemned heliocentrism.
‘Let us suppose, for the sake of argument, that we can refer “not improperly” to the initial singularity [the Big Bang] as an act of creation. What conclusions can we draw from it? That a Creator exists? Suppose still, for the sake of argument, that this, too, is conceded. The problem now is twofold. Is this creator theologically relevant? Can this creator serve the purpose of faith? My answer to the first question is decidedly negative. A creator proved by [Big Bang] cosmology is a cosmological agent that has none of the properties a believer attributes to God. Even supposing one can consistently say the cosmological creator is beyond space and time, this creature cannot be understood as a person or as the Word made flesh or as the Son of God come down to the world in order to save mankind. Pascal rightly referred to this latter Creator as the “God of Abraham, Isaac, and Jacob,” not of philosophers and scientists. To believe that cosmology proves the existence of a creator and then to attribute to this creator the properties of the Creation as a person is to make an illegitimate inference, to commit a category fallacy. My answer to the second question is also negative. Suppose we can grant what my answer to the first question intends to deny. That is, suppose we can understand the God of [Big Bang] cosmologists as the God of theologians and believers. Such a God cannot (and should not) serve the purpose of faith, because, being a God proved by cosmology he [or it] should be at the mercy of cosmology. Like any other scientific discipline that, to use Pope John Paul II’s words, proceeds with “methodological seriousness,” cosmology is always revisable. It might then happen that a creator proved on the basis of a theory will be refuted when that theory is refuted. Can the God of believers be exposed to the risk of such an inconsistent enterprise as science?’[1]
[1] Marcello Pera: The god of theologians and the god of astronomers, as found in The Cambridge Companion to Galileo, Cambridge University Press, 1998, pp.378-379. 'The heretic was denying an unambiguously defined doctrine of the Church (after it was defined), yet you brought him in as if he was an authority on that very doctrine' you said. Now Stanley, will you show us all the defined doctrine you are referring to?