My response:
One can thoroughly informed one's conscience in the teachings of the Pre-Conciliar Popes as well as the Saints and those eminent theologians and Prelates at the time who fought and criticized the New Rite of Mass predicting the harm the New Rite would do to souls. Even our current Pope once described it as a "banal, on the spot production".
Even Saints canonized after VCII such as St. Escriva refused to say the New Mass, obtaining a celebret to say the old.
For one steeped in the Traditions of the Church, it is quite possible to see that the New Mass would be so alien to the Catholic Faith practiced for 1960 years that one truly, in conscience, would decide to protect their Catholic faith, they could not attend. Attendance would indeed be morally impossible for them.
I ask you where you would draw the line yourselves? Is it morally permissible for you to attend a Mass with liturgical dance? Rock music? Scandalously dressed EM's? Mimes? Heretical hymns? Heretical homilies? Changing the words of the Mass? If there is any NO Mass you would not attend, you have made a moral judgment, as we all should. It just so happens that for many Traditional Catholics that line is drawn at attendance at any NO Mass. This line is drawn after much study and reflection of true Catholic theology, the NO Rite itself, the examples of Saints, and the tragic fruits the New Rite of Mass has produced in our time.