So, for instance, if a priest could offer a Traditional Mass at the main altar at St. Peter's, would you say it's wrong to do so because of the Novus Ordo desecration?
Well, if we believe that Malachi Martin's books are mostly factual, and if a satanic rite was done in St Peters, then yes, such a place is desecrated for the time being. But I can't prove this either way.
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If I were a priest, i'd not offer a latin mass in any novus ordo church, however beautiful it was, until some exorcism prayers were done and other blessings that a normal Trad priest could do on his own (presuming there was not a Trad bishop available to do something more substantial).
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I believe that a novus ordo is a sacrilege so I'm just being honest and logical, based on this foundational view. I could be wrong of course. But I think God would appreciate the caution used, even if my views were proven extreme.