With these two reactions, I seek not only to give the reactions to highly-respected orthodox clerics in the Church, but to highlight also their understandings of just how insidious this motu proprio really is. They both bring to bear their expertise on theology and canon law. First, I link to a treatise written by Cardinal Burke.
Note that in his first point, Cardinal Burke asks why the document wasn't written first in Latin. He then points out how an Italian word could be mistranslated into English. Whether or not he intended it, His Eminence illustrated Latin's value as a dead language.
Throughout his analysis, His Eminence comments on the alleged evils described in the motu, stating that in all his years of dealing with attendees of traditional Latin Masses, that he never saw the ills that the pope stated were such a threat. I'll leave the rest for your reading.
Taylor Marshall then deals with the statement that Archbishop Vigano made regarding the pope's obvious antipathy for the Latin Mass. The archbishop recommended to our reading an article by Massimo Viglione, entitled "The Hatred For The Mass Of All Time And The Question Of Obedience". The archbishop wrote the forward to that article. To be honest, I haven't yet had time to digest the article myself, but I trust the archbishop enough to believe that when he recommends it to our reading, then we should take him at his word. I also post Marshalls' commentary below.