Bishop Sanborn's entire rationale is flawed:
He claims that if Vatican II has changed the substance of Catholicism, you must become sedevacantist.
And if it has changed only accidents, you must become Conciliar.
Problem:
The docuмents of Vatican II are inherently ambiguous.
Therefore, it is not possible to determine whether they have changed the substance of the Church substantially, or only accidentally.
And since that is the case, the sedevacantists are in as much an erroneous position for their reaction as are the Conciliarists.
Oh, the wisdom of Archbishop Lefebvre!!
Recognize and resist is the only logical position.
PS: I was surprised to see him wearing a Conciliarist/Americanist "clergyman" suit instead of a cassock, and the Novus Ordo chain instead of a pectoral cross.