Monsignor Lefebvre is a hard topic for many to look at objectivly. There are hard feelings on both sides of the issues with many good points equally made. However, few people that comment on the SSPX really know the issues involved with their stand. There are plenty of false narratives about, but I think if you want to comment on the SSPX you must understand Marcel Lefebvre and the grave injustice done to him and the society from the beginning.
The following is an exerpt from Davies book, which you can read online in its entirety HERE
Apolgia Pro Marcel Lefebvre: The Campaign Against Écône
"On 26 March 1974 a meeting was convened in Rome to discuss the Priestly Fraternity of St. Pius X (which will be referred to hereafter simply as the Society of St. Pius X) and its principal foundation, the Seminary at Ecône.
Present at this meeting were Cardinal Garrone, Prefect of the Congregation for Catholic Education; Cardinal Wright, Prefect of the Congregation for the Clergy; Mgr. Mayer, Secretary of the Congregation for Religious; Mgr. Mamie, Bishop of Lausanne, Geneva, and Fribourg - the diocese in which the Society first obtained canonical authorization; Mgr. Adam, Bishop of Sion – the diocese in which Ecône is located. It was decided that a report on the Society and Seminary should be compiled.
With surprising speed the requested report was dispatched within four days, on 30 March 1974. It had been compiled by Mgr. Perroud, Vicar-General of the diocese of Lausanne, Geneva, and Fribourg. This report, accompanied by a letter from Bishop Mamie, was sent to Cardinal Garrone.
On 30 April 1974 Mgr. Lefebvre and Mgr. Mamie met at Fribourg.At some time in June 1974, Pope Paul is alleged to have convoked the ad hoc Commission of Cardinals. While it cannot be claimed with certainty that this is untrue, it is certain that the document convoking the Commission has never been produced. As will be shown later, this document was one of the items which Mgr. Lefebvre's advocate would have demanded to see had not the Archbishop's appeal been blocked. It is not unreasonable to presume that one reason why the Archbishop was denied due legal process was that a number of serious irregularities would have been brought to light. It can hardly be a coincidence, in view of the criticisms aroused by the doubtful legality of the proceedings against Mgr. Lefebvre, that when a Commission of Cardinals was convoked to examine the case of Fr. Louis Coache, a traditionalist priest who had been deprived of his parish for his defense of the traditional Mass and catechism, great care was taken to leave no legal loopholes. The text of this document will be cited under the date of 10 June 1975. It will also be made clear that not one shred of evidence proving that the Pope had approved of the action taken against the Archbishop and his Seminary was produced until 29 June 1975. Pope Paul stated in a letter of this date, which is included in its chronological order, that he had approved of the action taken against the Archbishop in forma specifica (this term will also be explained under the same date). It is not unreasonable to conclude that this was an attempt to give retrospective legality to what must certainly be one of the greatest travesties of justice in the history of the Church.
On 23 June 1974 the Commission of Cardinals met and decided upon a canonical visitation of the Seminary.
The Apostolic Visitation of the Seminary at Ecône took place from 11-13 November 1974. The two Visitors were both Belgians: Mgr. Descamps, a biblical scholar, and Mgr. Onclin, a canonist. The Apostolic Visitation was carried out with great thoroughness. Professors and students were subjected to searching and detailed questions concerning every aspect of life in the Seminary. However, considerable scandal was occasioned by opinions which the two Roman Visitors expressed in the presence of the students and staff. For, according to Mgr. Lefebvre, these two Visitors considered it normal and indeed inevitable that there should be a married clergy; they did not believe there was an immutable Truth; and they also had doubts concerning the traditional concept of our Lord 's Resurrection.1
On 21 November 1974, in reaction to the scandal occasioned by these opinions of the Apostolic Visitors, Mgr. Lefebvre considered it necessary to make clear where he stood in relation to the Rome represented by this attitude of mind. "This," he said, "was the origin of my Declaration which was, it is true, drawn up in a spirit of doubtlessly excessive indignation.”
In this Declaration he rejected the views expressed by the Visitors, even if they were currently acceptable in the Rome which the Visitors represented in an official capacity.
In this Declaration, he stated:
...we refuse...and have always refused to follow the Rome of Neo-Modernist and Neo-Protestant tendencies...No authority, not even the highest in the hierarchy, can compel us to abandon or diminish our Catholic faith, so clearly expressed and professed by the Church's Magisterium for nineteen centuries.
It is difficult to see how any orthodox Catholic could possibly disagree with Mgr. Lefebvre concerning this. It is all the more significant, therefore, that the Commission of Cardinals subsequently stated that the Declaration "seemed unacceptable to them on all points."
It is also important to note that this Declaration was not intended as a public statement, let alone as a Manifesto defying the Holy See. It was intended to be a private statement solely for the benefit of the members of the Society of Saint Pius X.
However, the Declaration was leaked without Mgr. Lefebvre's permission, and because the text, or extracts from it, were being used in a manner which he could not condone, he authorized Itinéraires to publish the full and authentic French text in January 1975. An English translation of this Declaration was published in Approaches 42-3 and The Remnant of 6 February 1975.
It is particularly significant that the Commission of Cardinals persistently refused to view this Declaration in the context of its origin: as a private reaction of righteous indignation to the scandal occasioned by the views propagated by the two Apostolic Visitors who had been sent to Ecône by the Commission of Cardinals.