You however are doing all kind of mental gymnastics.

Really, how so?

Learning about the history of a part of the Mass, and the principles of what it means to one in eccelesial communion and faith is "mental gymnastics"?

You have a dark outlook on learning Tom.

There should be no Una cuм question.

 Did you read the AI responses? 

Rather than opine that there should be no question, you should work on time travel theory and figure out how to go back and tell Pope Horsmodias, Pope Celestine II, and the priest of the cathedral at of Constantinople during the Nestorian heresy that, "there should be no Una cuм question.".

Fr. Wathen states it as the Church has always taught it.... "We say that their private judgement in the matter must not be introduced into the Liturgy which is an official act of the Church. Their private judgement has no place in the sacred liturgy."

Same as above, maybe Fr. Wathen can clarify the "AI bug" above and those pesky nuances of circuмstance and Catholic principles.

Public heresy is a PUBLIC act not private.
 
If you cannot recognize heresy you cannot recognize Catholic doctrine i.e.
 
"Holy Communion can be given to heretics (heresy)

Versus

"Holy Communion is only to be received by those in communion with the Rome and in a state of grace (doctrine)."

If you have moral certitude that the one is a manifestly public heretic then there are moral principles that oblige you to reject the heretic as being in communion with the Church.

Fr. Wathen and yourself will have to argue against those moral teachings.

You will also need to prove that Pope Celestine was wrong to praise the cathedral priest of Constantinople, and that the priest was wrong to remove Nestorius' name from the Canon before the Church's declaration of his heresy.

You and Fr. Wathen will have to argue against historical reality.

It is all right there in black and white above step by step for you to refute, it only took me about 60 seconds to ask the questions so maybe you can just click on the chat link at the top of the page and argue your Fr. Wathen points to it and it will agree with you. Then, depending on the answers it spits out, you may choose to come back here and share why the AI is "buggy". Basically you will have to prove Fr. Wathen's principle that, "their private judgement in the matter must not be introduced into the Liturgy.", is greater than the principle of what to do in the case of a manifestly, public, heretic "Pope" or local ordinary and how the Church expects one to act in the matter. Fr. Wathen's principle against the pre-Vatican II principles in the chat above I.e, "manifest public heretics are not members of the Church, a manifest public heretics separates himself from communion, the "Una cuм" in the Mass signifies eccelesial communion and unity in faith, that one must follow their convictions when founded on moral certitude (even if incorrect). etc. All those pre-Vatican II Catholic principles are outlined in the AI chat with references. I suppose you begin by refuting each one and showing us why/where they are actually false and.or condemned and that it is rather Fr. Wathen's principle that will always and singularily apply in EVERY circuмstance.

For me at least, that is what I would require to take you seriously on this point. 

Thanks!