the extreme view of Fr. Wathen, namely that the New Mass is supposedly "idolatry", "heresy", "blasphemy", always a "sacrilege", and a "mortal sin" etc.
If you go read the "Ottaviani Intervention", which was written by Cardinal Ottaviani (the top theologian in rome at the time), along with Cardinal Bacci and other theologians, you will see his (paraphrased) conclusions:
1. The new mass is a "striking departure from the Faith at Trent" (i.e. heresy).
2. The new mass' theology is anti-Trent (i.e. new religion/idolatry).
3. The new mass' consecration is "positively doubtful" (i.e. canon law states it is a mortal sin to attend doubtful sacraments, except in danger of death).
So, these Cardinals agreed with Fr Wathen's main points. And they were critiquing the "most pure form" of the new mass, before it had been released, post V2. These Cardinals were asked by Paul VI to analyze the new mass and give their opinions. They condemned it 100%.
The rest of Fr Wathen's condemnations (i.e. blasphemy and sacrilege) were confirmed AFTER the new mass was officially released, when the ACTUAL "mass" was much worse than the "pure form". The blasphemy/sacrilege came from 'communion-in-the-hand', the 'new age/community' antics of the "priests" and the gross irreverence/sacrilege of the "smells and bells" of this abomination.
So, yes, Fr Wathen was right. And many other of the "pioneer Trads" of the 70s/80s agreed with him.
The sspx was always wishy-washy on the new mass and still are.