So Lad, since this profession of the SSPX has been declared corporately and openly, and you have said this is open heresy, are the SSPX public heretics? If so, despite validity, shouldn't the faithful stay away from them?
I'm not quite sure where this idea originated that heresy is like "cooties" or something, that you can contact it by just showing up to receive the Sacraments from them. That's never been the case ... short of the Church declaring someone "vitandus". Trad clergy recieve the "ad hoc" jurisidiction to confer the Sacraments by virute of the faithful asking for them, and we have a right to receive them. We needn't punish ourselves for their errors and/or sins by depriving ourselves of the Sacraments.
Even receiving Holy Orders, up to and including Episcopal Consecration, from a heretic was not considered "ipso facto" heretical or even schismatic ... and was only made an excommunicable offense in the early 1950s as a deterrent against the Chinese Commie "Church", which of course Bergoglio and Prevost have endorsed. Essentially, any reasonably just cause, i.e. if one has no other alterantive to receive nourishment from the Sacraments, would justify attending their Masses. So, when +Cushing openly rejected EENS dogma, where Catholics required to avoid his Masses, or would they have committed grave sin by failing to fulfill their Sunday obligation? Clearly the latter.
Now, it would require a rather more grave reaosn to receive Sacraments from a declared schismatic / heretic, like the Orthodox, but it's not against divine law, as even Pope St. Pius X permitted Catholics in Orthodox areas to receive Sacraments from them. In fact, the Church has power over the Sacraments adn can (and does) command all priests to distribute Sacraments to the faithful Catholics, regardless of what heresy, schism, error, or public sin they adhere to or are mired in.