Father Z discusses two fairly elementary points, although many Catholics get them wrong:
Criticism of the Pope can become a mortal sin if one’s criticism is filled with a hatred and vitriol that shows a lack of respect or filial love for Our Sovereign Pontiff. One must also consider to whom you show that lack of respect. If by your words and actions you harm his reputation with others unjustly, you do him and them a grave wrong. You also may be committing the sin of sacrilege.
But be careful in aiming criticism at the Pope. Be careful to whom you open your mind or reveal your attitude. Examine your conscience with brutal honesty, remembering that His Holiness has a perspective on the Church that we do not.
Go here to read the comments. Another elementary point is that when the Pope gives an opinion outside of the realm of faith and morals, he has not charism that entitles his opinion to any special weight. Some prominent Catholic bloggers think otherwise (Mark Shea that is your cue):
So, in answer to the question of how Catholics should navigate the massive areas of life where the Church offers us wisdom, but not infallibility, I think the sound approach is summed up in the frightening-to-Westerners word “docility”. We should assume that, unless there is very strong evidence to the contrary, a Magisterium teacher speaking by virtue of his office is basically is doing what they have ever done–articulating the teaching of the Church and giving broad and basically reliable advice on how to apply that teaching practically (along with lots of caveats about how this applies “in most cases” or “assuming the current science is accurate” or “if what the experts say about global warming or the Laffer Curve or the effects of gamma rays on Man-in-the-Moon Marigolds or the situation in Gaza or the abortifacient qualities of morning-after pills is true”).
The problem with that attitude is that Popes contradict each other quite a bit in these areas and that it reduces Catholicism to blindly following every word uttered by the current Pope. Catholic history indicates that this is simply not how many faithful Catholics, including saints, have acted when a Pope fell into error.
“Peter has no need of our lies or flattery. Those who blindly and indiscriminately defend every decision of the Supreme Pontiff are the very ones who do most to undermine the authority of the Holy See—they destroy instead of strengthening its foundations” – Fr. Melchior Cano O.P., Bishop and Theologian of the Council of Trent.