His Highness acknowledges your argument, but rejects it on the grounds that it less-plausible to believe that the SSPX is in schism, rather than the contrary.
Fr. Gianfranco Ghirlanda, SJ, who acted as the general editor of the Code of Canon Law noted in his commentary Il Diritto nella Chiesa that "The schismatics, insofar as duties and rights are concerned, find themselves in a situation similar to the apostates and heretics, in that they also [the scismatics] are under excommunication."1 Yet, it is clear that, in the case of the SSPX, this is not the case, since they have been - per Misericordia et Miseria - given such rights and duties by the Church in the exercise of confession (and then, also for marriages). There have been other minor instances, but most of them bore His Highness and so he does not spend much time on them.
The Theologians of the Kingdom, therefore, point out that, if the SSPX is in schism, it is undeniable that they would be unique among schismatic groups. Not even the Orthodox are given such rights and duties (they have none under canon law). It is further undeniable that this unique position among schematic groups, if it exists, is not yet provided for under Canon Law. Consequently, His Highness invites the eminent Edwardus to consider whether the position of the SSPX does not have more in common with an institute in the Church, rather than one foreign to it.
As such, the MUCK proposes that it is more plausible to say that the Mass of the SSPX is not schismatic, and therefore included in the merits of Christ.
1"Gli scismatici, per quello che riguarda l’adempimento degli obblighi e l’esercizio dei diritti, si trovano in una situazione simile a quella degli apostate e degli eretici, in quanto anch’essi sono colpiti da scomunica" (c.f. canon 1364).
Ex cathedra regis