So just as one is subject to the laws of their state even if they do not agree with them every Christian is subject to the Roman Pontiff.
This is a sophist spin if i ever saw one, but which is another illustration of the interpretative nature even of some infallible teaching.
Your explanation ignores the context which defines what is meant by "subject," as well as other historical teachings which define what membership means
“We declare, say, define, and pronounce [ex cathedra] that it is absolutely necessary for the salvation of every human creature to be subject to the Roman Pontiff.”
Boniface thus makes "subject" to mean commitment to the papacy and successors, which they were judged not to be by certain dissent.
Likewise
Pope Pius XI, Mortalium Animos: Furthermore, in this one Church of Christ no man can be or remain who does not accept, recognize and obey the authority and supremacy of Peter and his legitimate successors. Did not the ancestors of those who are now entangled in the errors of Photius [the eastern “Orthodox” schismatics] and the reformers, obey the Bishop of Rome, the chief shepherd of souls?...Let none delude himself with obstinate wrangling. For life and salvation are here concerned...”
Rendering subjection to the Roman pontiff and being part of the Church as inclusively meaning such as do not/will not accept, recognize and obey the authority and supremacy of Peter and his legitimate successors, is part of that obstinate wrangling.
"The practice of the Church has always been the same, as is shown by the unanimous teaching of the Fathers, who were wont to hold as outside Catholic communion, and alien to the Church, whoever would recede in the least degree from any point of doctrine proposed by her authoritative MagisteriumSatis Cognitum (# 9): June 29, 1896: ."
Likewise the Fifth Lateran Council defines that 'subjection to the Roman pontiff is necessary for salvation for all Christ's faithful, as we are taught by the testimony of both sacred scripture and the holy fathers, and as is declared by the constitution of pope Boniface VIII of happy memory" means the obedience it goes on to enjoin.
Moreover, making properly (trinitarian) baptized Prots members of the Catholics church makes the words of the Seventeenth Ecumenical Council (Florence) to be of one effect, or merely speaking of a hypothetical group:
"The sacrosanct Roman Church...firmly believes, professes, and proclaims that..not only pagans, but also Jews and heretics and schismatics cannot become participants in eternal life but will depart `into everlasting fire...unless before the end of life the same have been added to the flock;
It is thus clear that required membership in Christ's Church and subjection to the Roman Pontiff meant obedience to him, versus dissent, and thus would exclude those "who honor Sacred Scripture, taking it as a norm of belief and a pattern of life... within their own Churches or ecclesiastical [Protestant] communities…" as being joined a certain communion with Caths in the Holy Spirit, who "with good reason are accepted as brothers by the children of the Catholic Church” under the premise that "all who have been justified by Faith in Baptism are incorporated into Christ."
The SSPX and SSPV traditionalists are correct on this one, though just as wrong as their brethren in many other Cath error s. .
Thank you for pinging me to that extremely informative and pertinent post. I hung on every word. Your research is amazing. It just never occurred to me that there was more to the Boniface viii pronouncement than was already posted. The context is crucial. When, with God’s help, I am able to make a more significant contribution to this discussion, your input will be invaluable. Thanks again.