I think the example of Bp Fellay and Fr Pagliarani vs Fr Gruner is an important distinction. Bp Fellay represents the SSPX invariably. He was SG for 24 years, a Catholic Bishop in said Society for now 31 years so he really physically represents in a way (at least should represent, or maybe used to represent is more accurate) the resistance to VII and the NO and his presence at a conference should say something about the conferences status about those subjects. Now obviously he will be speaking at the Angelus Press conference where a NO presbyter who loves “St” JPII and his vulgar ToB will also give a talk. And that in and of itself says something.
Fr Gruner never represented a group outside of the Fatima Center which wasn’t founded on resistance of VII and the NO outright, but on promoting the full message of Fatima. Of course we all know he shot down VII and the NO as well but it wasn’t his primary message, whereas the SSPX has shown (historically) their open resistance to the changes. Fr Gruner worked with anyone (the SSPX, FSSP, Resistance, NO, everyone) who supported the full message of Fatima, and the SSPX had always worked with people who wanted undiluted Catholicism with novelty. Obviously pro-life movements aren’t directly religious as being against murder is the natural law and written on all men’s hearts regardless of creed, and is quite dominated by Protestants, but our presence as a pro-life rally isn’t a Protestant service, it’s a rally against the murder of babies. My wife and I have attended them where they have had Prots, NO, whoever, and we just stick together and pray our Rosary and move on.