I don’t think so:
The SSPX had no problem speaking out against modernism from 1970-2012, so RR cannot be a cause of silence (unless you’re saying that they largely dropped the second R, and that’s the cause of silence...in which case I would agree).
One could argue that it's indirectly the cause of the silence. When you hold that a man is the legitimate Vicar of Christ, the
sensus Catholicus inexorably draws Catholics to attempt to be in submission to and in communion with the Vicar of Christ.
In other words, the refusal to at least QUESTION and DOUBT the legitimacy of the V2 papal claimants led to the negotiations and attempts at reconciliation, which then in turn led to their not publicly criticizing them or making statements that might jeopardize the reunification movement.
If I were certain that Bergoglio is the pope, I would have been back in communion with him somehow ... yesterday, whether it's in the Eastern Rite or FSSP/Motu (and their "legitimacy" would also guarantee for me that their Holy Orders are not doubtful, for the Church cannot promulgate invalid Sacramental Rites).
Conversely, given that their legitimacy is highly doubtful, and it's much more possible that these are non- and anti- Catholic Antipopes, I wouldn't feel the least bit inclined toward seeking any kind of reconciliation with them, but would view them as mortal enemies of the faith.
Regardless of your opinion on some of these issues, it can't be denied that the Catholic instinct (
sensus) strongly draws Catholics toward submission to the Pope. Those who have no concern whatsoever with being separated from the Vicar of Christ either 1) (at least secretly) harbor doubts about their legitimacy or 2) have had their Catholic sensibilities eroded so badly that they have completely extinguished this eminently-Catholic sensibility. And that latter is precisely why I've been so vocal of this particular articulation of R&R that's been made here on CI.
Archbishop Lefebvre retained that sensibility:
“Now some priests (even some priests in the Society) say that we Catholics need not worry about what is happening in the Vatican; we have the true sacraments, the true Mass, the true doctrine, so why worry about whether the pope is heretic or an impostor or whatever; it is of no importance to us. But I think that is not true. If any man is important in the Church it is the pope.” (Talk, March 30 and April 18, 1986, text published in The Angelus, July 1986)
And yet many modern R&R have in fact adopted this stance that the pope question is not particularly important. Believing him to be the pope, the attitude of "Who cares what he teaches?" is completely alien and contrary to a core Catholic sensibility, the one sensibility in fact which distinguishes a Catholic from an Old Catholic, Eastern Orthodox schismatic, or even Protestant.