Well, I tried to access the link, but I get an "The authors have deleted this blog" message. But I've read similar publications including, if I recall right, from FSSP clergy. The points raised by articles such as those was what led me to think that the Council could be read "in the light of Tradition", to use Archbishop Lefebvre's own phrase in describing the problems it raised. The historical example of Magisterial teaching on usury shows by analogy that sometimes it is not clear to all involved
Consider the two statements.
A: There is an absolute right without any corresponding obligation to hold and teach any error of one's choosing.
B: There is a limited right to seek the truth freely in order that one might fulfill one's obligation to know, embrace and obey the truth.
While each may be called "religious liberty", it should be apparent they are talking of diametrically opposite things.
Now, it is agreed by all involved that error may be tolerated.
Thus the two principles are clarified to which recourse must be had in concrete cases for the answer to the serious question concerning the attitude which the jurist, the statesman and the sovereign Catholic state is to adopt in consideration of the community of nations in regard to a formula of religious and moral toleration as described above. First: that which does not correspond to truth or to the norm of morality objectively has no right to exist, to be spread or to be activated. Secondly: failure to impede this with civil laws and coercive measures can nevertheless be justified in the interests of a higher and more general good.
As to the other point, if the question is whether there can be a moral or natural right to error, the answer must be unequivocally in the negative. There can be no right to do wrong, and to say otherwise is nonsensical and condemned by the traditional Magisterium. Both SSPX and FSSP agree with this.
But did the Second Vatican Council say there is a natural right to error? Here the SSPX usually answers yes and the FSSP usually answers no. At issue is the following passage
It is in accordance with their dignity as persons-that is, beings endowed with reason and free will and therefore privileged to bear personal responsibility-that all men should be at once impelled by nature and also bound by a moral obligation to seek the truth, especially religious truth. They are also bound to adhere to the truth, once it is known, and to order their whole lives in accord with the demands of truth. However, men cannot discharge these obligations in a manner in keeping with their own nature unless they enjoy immunity from external coercion as well as psychological freedom. Therefore the right to religious freedom has its foundation not in the subjective disposition of the person, but in his very nature.
St.Thomas says something interesting in answering the question of whether the children of Jєωs or other unbelievers should be baptized against their parent's will. After answering no, he says it would be contrary to natural justice.
Whatever it is, I don't think anyone is accusing anyone else of setting up strawman. Archbishop Lefebvre often asked this specific question to Pope Paul VI, but it was ignored. The 1994 Catechism, though, answers in the negative.
The recent SSPX public response to Rome, I think it was by Fr.Gleize, to Msgr.Ocariz framed the question clearly and cogently, presenting the Magisterial texts of the past. Should a definitive answer come, the SSPX will regard it as a correction, the FSSP as a clarification. As TKGS says, though, much of the hierarchy currently undoubtedly holds a wrong understanding, so it can hardly be said to be unimportant for the future of the Church.