I don't believe a person who denies BoD has any idea at all what the Magisterium is.
It is the living voice of God on earth, and therefore you eaither must attribute the Promulgated Missale Romanum of Paul VI as an act of Christ's will for his Church or deny the authority issuing it. It's really all that is available to you, otherwise you charge the Church with handing down harmful disciplines, which is condemned by Pope Pius VI.
Which will it be?
The mass of PPVI obviously is not an act of Christ's will for His Church, yet PPVI promulgated it using his authority along with the authority of the hierarchy because there was nothing to stop him - no one should ever accuse the Church, which is Christ, of handing down harmful disciplines.
The people who went along with the new religion, those who helped further the destruction wrought by the hierarchy of the day, they were the ones who compromised the faith for themselves and their children - and they did so of their own free will, they'll never be able to blame anyone but themselves for losing their faith. Many of them did so while using the excuse that they did so in "obedience to the pope and the magisterium" - but before God, such a farce of a reason will never relieve them of their guilt in the matter.
The flavor of the day was
"if the pope said to do it then blindly, we must do it". So many people believed this lie because that is what they were taught. These days that same polluted mentality prevails - I attribute that mentality in large part to the half truths taught by certain "well respected" 19th/20th century theologians, whose false teachings have been embraced as if they are authentic teachings of the Church
.In the words of +ABL:
"After all of these liberal ideas have been infiltrated into the seminaries, the catechisms and all the manifestations of the church, I am now being asked to align myself with these liberal ideas."