Bishop Sanborn:
Bingo.
Right. I've made this same point repeatedly. One can quibble about the precise extent of infallibility, but this is a question of the Church's indefectibility. To say that an Ecuмenical Council of the Church can lead to the creation of a parallel anti-Church is contrary to the overall indefectibility of the Magisterium and of the Church as a whole. To say that the Church can promulgate and use a Rite of Mass that displeases God (a Protestantized/paganized Mass as Vigano calls it) and cannot be attended by Catholics in good conscience is contrary to the Church's disciplinary infallibility.
R&R who keep pushing the narrow view of infallibility are missing the forest for the trees. Sedevacantists often overreact to this error by promoting an extreme view of infallibility that goes too far, when the battle needs to be waged on the level of indefectibility.
I immediately noticed that the logical trajectory of +Vigano's June 9th letter is toward sedevacantism. Thus far he has held back, instead using the same infallibility argument used by R&R.