Pope Eugenius IV, A.D. 1431-1447, at Council of Florence *** allegedly INFALLIBLE***: allegedly Ex cathedra: "It [the Holy, Catholic, and Apostolic Church] firmly believes, professes, and proclaims that none of those outside the Catholic Church, not only pagans, but neither Jews, nor heretics and schismatics, can become participants in eternal life, but will depart “into everlasting fire which was prepared for the devil and his angels”
[Matt. 25:41], unless before the end of life they have been added to the Church; and that the unity of the ecclesiastical body is so strong that only to those remaining in it are the sacraments of the Church of benefit for salvation, and do fastings, almsgiving, and other functions of piety and exercises of Christian service produce eternal reward, and that no one,
whatever almsgiving he has practised, even if he has shed [his] blood for the name of Christ, can be saved, unless he has remained in the bosom and unity of the Catholic Church." (Cantate Domino, A.D. 1442)
I’ve also been told from radical traditionalist Catholics that the prevatican II theology manuals said that it is mortal sin to attend worship services that are heretical and they sharply accuse Pope Bennedict for taking of His shoes, facing east, and praying with muslims in a mosque.
Does anyone have ideas how to refute this if it comes up?