"To what extent can a Catholic disregard the Church’s moral & social teaching and still remain in full communion with the Church? The anathemas of Trent, and the other ecumenical councils, were quite clear on a number of doctrinal issues. For example, no true Catholic can deny the real presence of Christ in the Eucharist, or Baptismal Regeneration, or the Immaculate Conception of Mary. But since many of the social doctrines of the Church have no clear “anathema” of an ecumenical council for those who would oppose them, some seem to think that these doctrines are still therefore “up for grabs.” This is in spite of the fact that the affirmation of a “right” to abortion or the admission of homosexual couples to the sacrament of Matrimony would not only mark a complete break from Tradition, but would actually contradict everything that the Church taught on these subjects for the first 1900 years. I know it’s not likely that secular figures will ever agree with the Church’s position on some issues, but how can the Church best address the dissent that comes from within?"
Question 2: Because I used to dissent from the Church's social teaching on abortion as it relates to the legality of procuring an abortion and changed my mind years later, I have some personal experience in what works to bring someone to a point at which they can understand the Church's teaching and assent to it. I don't think my experience can be straightforwardly generalized into a formula for bringing people to that point; I will simply lay out some strategies that do not work well and others that seem to have a chance to be more productive.
First, let's examine some strategies that I've seen fail miserably over and over. One of the most common ways I've seen people address other individuals who dissent from Church teaching on controversial political topics in the West (i.e. abortion, same-sex marriage, the death penalty, euthanasia, immigration policy, etc.) is to advise them that they cannot vote for members of a particular party and be Catholic. Or that they cannot hold to a particular political philosophy and be Catholic.
This is sometimes followed by an insistence that the person addressing someone else's dissent has found the right party's members to vote for or the right political philosophy that all Catholics should adopt. I've never seen this work, at least not in the short term and a quick response to dissent. People do occasionally make large changes to their political beliefs and party affiliations, but it generally happens over the course of months or years rather than over the course of one or two conversations, and so rapidly informing someone that they're wrong about all that stuff and that you have the right answers generally doesn't lead anywhere productive.
Of course, even people who take a long-term approach to dialogue with those who openly dissent from Church teaching often still manage to do a poor job of it for much the same reasons. A long-term dialogue in which a person maintains that only those who hold to one particular political philosophy or votes for members of one particular party is also very unlikely to be productive.
Going for the best chance at productive dialogue with those who dissent means that we have to admit that there is a range of political philosophies that can be coherent with Church teaching and that we generally don't have a political party in the West that conveniently lines up perfectly with Church teaching. If we don't admit these inconvenient truths, any dialogue we have with someone who dissents (including ourselves) is likely to be frustrated because it appears that we are just being rankly partisan or fanatical about our own political philosophies.
Once we've learned to steer clear of those common pitfalls, we are in a better position to dialogue with someone who is dissenting from Church teaching for political reasons. But we still have a lot of work to do. The first step in that work could well be showing them how to make their existing political philosophy more coherent with Church teaching. Or by showing them examples of people of high integrity who assent to the Church's teaching while still being a member of their preferred political party.
When someone is walking toward a cliff, we don't have to immediately drag them back a few hundred feet and rough them up in the process. Getting someone to take one step away from the cliff is a good start. And when someone is walking toward the cliff, the smart thing to do is not to run up behind them and tackle them to the ground, but rather to invite them over for a nice cup of tea.
In the same way, my experience is that it's much more effective to address those who dissent from Church teaching by means of helping them take small steps away from dissent and positive invitations to explore ways of engaging in political philosophy that are both rational and compassionate.
This was not, by the way, how my friends approached helping me work through my dissent from Church teaching. The tactic I've described didn't work on me, but it might have if it had been tried. Or more likely not, primarily because I'm unusually stubborn and independent. My friends confronted me in a much more argumentative way, which is a perfectly fine way of dealing with me because I don't get angry and shut down in the face of opposing arguments. I consider them at length, come to a preliminary conclusion, and then consider them again after I have more data.
But because most people don't process arguments the way I do, I don't recommend the approach that was helpful for me to use as a strategy for everyone else. If you do use it, make sure you know the person as well as my friends knew me. Specifically, make sure they are comfortable with robust arguments that don't necessarily respect their feelings.
Question 1: I'm not sure how my friends knew that I was dissenting from Church teaching, but I can certainly hazard a guess. I was openly taking the position that abortion should be legal despite the Church's teaching that it's murder in most cases (murder already being illegal). And I was stubbornly insisting that there was not a problem with me doing so, holding the position for several years. In hindsight, it is pretty clear to me now that others could have reasonably concluded that I was in a state of heresy on the topic.
It's not always an easy thing to determine when someone is in a state of heresy. I've written at some length before on the difficulties of doing so, and they require us to spend some time and effort rather than just writing off anyone who disagrees with our understanding of what the Church teaches as a heretic. It's very easy to fall into the trap of thinking that our own overly simplistic understanding of Catholic teaching is the only correct one, or that our philosophical methods are the only ones allowed, or that our political views are the only ones that could be compatible with Church teaching.
Those things tend to lead us to over-diagnose others of catching the contagion of heresy. And this is especially complicated in the case of the intersection of politics and Church teaching because Jesus didn't provide us with a political philosophy or ideology. Nor has the Church always had the same relationship with every instance of an empire or a state. And even the Code of Canon Law doesn't provide easy answers to these questions, as canon lawyer Edward Peters points out in his piece on Joe Biden's decision to officiate a same-sex wedding.
While it's difficult to map out a clear line over which one cannot step without incurring a latae sententiae excommunication for heresy, some people do manage to run past the line so fast and so far that it's fairly obvious that they have long since crossed the line. When someone demonstrates that they are aware that they believe something which contradicts Church teaching and publicly speaks on that point for years with no sign of attempting to assent to Church teaching, it's a fairly obvious case.
Many cases are not so obvious, and my own personal experience helped me to realize something relevant to this state of affairs: I have no idea at what point I became a heretic. It was pretty clear at a certain point, but there was no flashing sign along the way that said, "Welcome to Heresyville!" at the border of the Excommunication Township. That's why I'm very reluctant to propose that someone ought to be excommunicated or that they hold heretical beliefs on a particular topic.
It's not that I don't think plenty of people may well be heretics, but that I doubt my own ability to judge that accurately without a mountain of evidence piled up. And this is especially true when the additional difficulties of the relationship between Church teaching and public policy are added into the analysis. Are there a few people (including me) who have run so far past the line that I can be fairly sure they meet the precise technical definition of the word heretic? Sure.
That said, outside of those cases, I give people the benefit of the doubt and try to have a productive dialogue with them in such a way that they can see that it's possible to have political views that are coherent with Church teaching and that it's a good thing for Catholics to do. And even when the person is clearly a heretic with regard to a particular topic (or several), it helps to remember my own heresy and remain humble in how I approach that person about the matter.