The intent is obtaining and building sanctifying grace. The undesired and unavoidable result is that there is an objectionable line in that Mass said by a Priest that Catholic charity must presume is acting in good conscience.

That doesn't mean you have to partake of what you know to be an objective sacrilege.  Why do you assume that there is grace there?  The same logic could have kept people going to the Novus Ordo.  I prefer to take my chances without the sacraments for now, but keeping the faith whole and undefiled.

If a priest was giving a Requiem Mass for Che Guevara, would you attend that while holding your nose?  Your attendance at a sacrilegious Mass makes you complicit, John G.

I am aware that the situation is somewhat more complex with the "Popes" than it would be with this sacrilegious Requiem Mass, but it is not as complex as the matter of the Popes at the time of the Schism.  Neither Popes nor anti-Popes at that time were public, manifest heretics, nor had they publicly taught error and heresy in encyclicals.

It is really quite simple but we make it complex.  If you believe that the Pope can teach heresy in an encyclical, and that he is not covered by infallibility in that happenstance, nevertheless you can and should avoid the una cuм Mass for the simple reason that Benedict is a heresiarch.  

According to cuм Ex Apostolatus you are totally absolved from any attachment to this "Pope," and from any attachment to those who are attached to him -- that means SSPX or independent priests who say the una cuм -- even if it turns out you're wrong and through some miracle he remained technically a Pope like Honorius ( whose crime was infinitesimal in comparison ).  Because he is undeniably a heretic.  I for one will have no portion with blatant formal anti-Christ heretics.