Putting aside the difficulty that "supplied jurisdiction" claimed in one's own favor is a very complex and dangerous issue in itself, the fact is the SSPX has absolutely no jurisdiction, supplied or otherwise, to stand in judgment over the validity of annulments granted by ordinaries in their own dioceses. Never in the history of the Church has such a usurpation of the local ordinary's authority ever been countenanced.
I disagree the consecrations were grave breaches of discipline.
Then we need to define grave. We are talking here about meddling with the very means of the Apostolic Succession, not dispensing someone from a fast.
This Pontiff is routinely disobeyed by prelates--in matters of far greater importance.
Surely you recognize the inherent weakness of this argument. Just because someone else does something wrong and gets away with it, one is not justified in one's own transgression by theirs.
One can argue that the Holy See has been capricious in its censure - and one would have a point.
But that does not justify disobedience.
Aquinas and Bellarmine both argue that no Pontiff may command what would harm the Church, insisting that disobedience in the face of such a command would be legitimate.
You are reaching here. One could validly argue that appointing Fr. Jones over Parish X is harmful to the Church and that Fr. Smith is a much better candidate for that parish. Almost any action by any Pope could be interpreted as harmful to the Church in some way. Who is to judge? You?
The fact is that Lefebvre did something objectively wrong and disobedient, but he did it according to the dictates of his conscience.
Abp. Lefebvre would gladly have apologized and spent his life in sackcloth and ashes atoning for his disobedience in this matter if the Pope had required it as a condition for preserving the Church's liturgical and theological traditions.
Williamson is unwilling to even admit that his consecration was disobedient.
It is this attitude of Williamson's which excites a visceral repulsion for the SSPX intransigents among obedient Catholics who labor for the preservation of our cultural traditions within the canonical norms of the Church.
To the extent that individual SSPXers follow Williamson's example they will injure the Body of Christ.