Further, all those things are to be believed with divine and Catholic faith which are contained in the Word of God, written or handed down, and which the Church, either by a solemn judgment, or by her ordinary and universal magisterium, proposes for belief as having been divinely revealed. And since, without faith, it is impossible to please God, and to attain to the fellowship of his children, therefore without faith no one has ever attained justification, nor will any one obtain eternal life unless he shall have persevered in faith unto the end...The first condition of salvation is to keep the rule of the true faith.
If any one, therefore, shall say that blessed Peter the Apostle was not appointed the Prince of all the Apostles and the visible Head of the whole Church militant; or that the same directly and immediately received from the same our Lord Jesus Christ a primacy of honor only, and not of true and proper jurisdiction: let him be anathema.
If, then, any should deny that it is by institution of Christ the Lord, or by divine right, that blessed Peter should have a perpetual line of successors in the Primacy over the universal Church, or that the Roman Pontiff is the successor of blessed Peter in this primacy: let him be anathema.
We teach and define that it is a dogma divinely revealed: that the Roman Pontiff, when he speaks ex cathedra, that is, when in discharge of the office of pastor and doctor of all Christians, by virtue of his supreme Apostolic authority, he defines a doctrine regarding faith and morals to be held by the universal Church, by the divine assistance promised to him in blessed Peter, is possessed of that infallibility with which the divine redeemer willed that his Church should be endowed for defining doctrine regarding faith or morals; and that therefore such definitions of the Roman Pontiff are irreformable of themselves, and not from the consent of the Church. But if any one—which may God avert—presume to contradict this our definition: let him be anathema.
This is the teaching of Catholic truth, from which no one can deviate without loss of faith and salvation (Philip Schaff, The Creeds of Christendom (New York: Harper, 1877), Dogmatic Decrees of the Vatican Council, On Faith, Chapter III; Chp. 4, pp. 266-71).
Vatican II
This sacred Synod turns its attention first to the Catholic faithful. Basing itself upon sacred Scripture and tradition, it teaches that the Church, now sojourning on earth as an exile, is necessary for salvation. For Christ, made present to us in His body, which is the Church, is the one Mediator and the unique Way of salvation. In explicit terms He Himself affirmed the necessity of faith and baptism (cf. Mk 16:16; Jn. 3:5) and thereby affirmed also the necessity of the Church, for through baptism as through a door men enter the Church. Whosoever, therefore, knowing that the Catholic Church was made necessary by God through Jesus Christ, would refuse to enter her or to remain in her could not be saved. (Your point)
When the Vatican rescinds Vatican I please post the declaration.
Good heavens, son, take two aspirins and go to bed. Anathema is NOT condemnation to hell. It's just an indication of incredibly erroneous thinking.
Now, read that sentence carefully and slowly.
As a Christian, would you say that if someone prayerfully came to the conviction that the Catholic was made necessary by God through Jesus Christ, but would choose to disobey what they had concluded was the objective will of God in order to do something else because they wanted it more than they wanted to do the will of God ... would you say that such a person can be saved?
And what does that have to do with Protestants? Do many Protestants sincerely believe that becoming Catholic is necessary for their salvation, yet refuse to do so?