Sean,
According to you, is the New Mass poison (as pointed out repeatedly by Archbishop Lefebvre and as was always the position of the SSPX for a number of years - as you surely can attest to) or is it nourishment (as Bishop Williamson says)?
Hodie-
As pointed out by Archbishop Lefebvre in the quote you ignored, it is both:
It is like poisoned meat which will kill you in the long run, but which nevertheless gives nourishment despite the poison in the short term (therefore only those in necessity can eat it).
That position is identical to Bishop Williamson’s own.
We often use the example of the poison cake: it contains rat poison (arsenic), but it won’t kill you in a single dose, and provides calories (nourishment) despite the poison.
Obviously only a desperate starving person would/could eat such a cake, knowing it will make them sick (and eventually kill them).
Same with the new Mass.