If we deny that the Church has such a gift [a gift (or charism) of infallibility in matters of faith and morals], then we are left with a subjective, individualistic, “changes hearts” criterion of canonicity, and such a subjective criterion is, as you say, bogus.(source)
This false dichotomy is fairly easily smoked out.
It can be smoked out a few ways.
I. Historical Example
The Roman church did not claim to infallibly define the canon of Scripture before Trent, and yet people (both in the Roman communion and outside it) felt perfectly comfortable having a fallible canon. It worked for over 1500 years.
Ignatius was satisfied with a canon that was not based on a church having a gift of infallibility. So were all the church fathers and all the medieval theologians.
The North African councils produced a canon themselves rather than attempting to seek an ecumenical decision on the question. Before them, Athanasius provided a list of the canon of Scripture without even relying on a church council!
And then, after the Reformation comes along, Trent tries to infallibly define the canon. And when they define it, they contradict two leading cardinals of the immediately previous generation (Cardinals Ximenez and Cajetan) - cardinals who affirmed Jerome's (and the Protestants') canon.
II. Analogical Counter-Example
What Bryan is arguing for on the level of books is also an issue with respect to parts of books - to the issue of the text of the books themselves. Is the story of the woman found in adultery in the original text? Is the famous passage in 1 John 5:7-8 part of the original text?
Bryan could try to argue that "If we deny that the Church has such a gift [a gift (or charism) of infallibility in matters of faith and morals], then we are left with a subjective, individualistic, “changes hearts” criterion of [textual authenticity], and such a subjective criterion is, as you say, bogus."
But it should be readily apparent that one can have a knowledge of the text of Scripture and reach conclusions of textual authenticity without resorting to completely subjective and individualistic exercises of authority.
Trent itself originally attempted to define not only the books themselves but also the parts of books (with a focus on things like the apocryphal additions to Daniel and Esther). However, Rome has subsequently issued a New Vulgate that does not entirely follow the text of the Clementine Vulgate.
III. Logical Analysis
Obviously, the portion of Bryan's comment I've quoted above is simply a fragment of a larger argument. As such, it is a little informal. On the one hand, we could simply insist that Bryan should formalize his argument. However, until he does so, we can explore his argument in the form in which it has been presented.
As presented, it seems to suggest that there are really only two options:
1) Infallible Church
2) Subjective, Individualistic Judgment
This set is not well-defined. At least, it does not appear to be well-defined.
Is our knowledge of the facts of history generally simply a matter of subjective, individualistic judgment? Is our knowledge of which books Homer wrote the domain of subjective, individualistic judgment? Is our knowledge of which are the previous presidents of the United States merely a matter of subjective, individualistic judgment?
Unless the words "subjective" and "individualistic" are simply epithets (which is a real possibility), then there is a third way - a way in which we conclude that historical facts (God inspiring 66 books, Homer composing two epic poems, 40+ men becoming president of the U.S.) are true, without either resorting to subjective, individualistic means or relying on an infallible church.
IV. Scriptural Analysis
Scripture does not, of course, directly address Bryan's complaint. However, Scripture does provide teachings that undermine Bryan's complaint.
One of the areas of teaching relates to the fact that the elect, upon regeneration, are sheep that hear the voice of the shepherd:
John 10:16 And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd.
John 10:27 My sheep hear my voice, and I know them, and they follow me:
For he is our God; and we are the people of his pasture, and the sheep of his hand. To day if ye will hear his voice,harden not your heart, as in the provocation, and as in the day of temptation in the wilderness: when your fathers tempted me, proved me, and saw my work.
Bryan cannot deny that the Scriptures are the voice of the Shepherd, and consequently we conclude that the elect will recognize and follow the Scripture. This does not mean that they will always do this perfectly. They remain human and fallible. There have been great men of God who have erred with respect either to rejecting an inspired book or accepting as inspired a book that is not.
Deuteronomy 33:3 Yea, he loved the people; all his saints are in thy hand: and they sat down at thy feet; every one shall receive of thy words.
John 17:8 For I have given unto them the words which thou gavest me; and they have received them, and have known surely that I came out from thee, and they have believed that thou didst send me.
1 Thessalonians 2:13 For this cause also thank we God without ceasing, because, when ye received the word of God which ye heard of us, ye received it not as the word of men, but as it is in truth, the word of God, which effectually worketh also in you that believe.
The point here is that the people of God do receive the Word of God. That's true whether it is in preached form (as in a sermon that conveys the Word of God) or in written form (principally in the Scriptures).
This recognition of God's word for what it is, a recognition that the Holy Spirit gives to all believers to a greater or lesser degree, does not translate into an infallible ability. The Thessalonians were fallible human beings. Nevertheless, they were able to receive Paul's message for what it was. According to the same principle, we can receive the Scriptures for what they are.