Same argument as the Mormons and other cults. Under sola ecclesia, in which the church alone is the supreme authority, as it alone is assuredly right in defining what Scripture and tradition consists of and means, then all sorts of things not seen in Scripture, and even what is contrary to it (which the church defines as not doing so), can be said to be binding Truth.
Mormonism has its fables, and Catholicism has theirs.
But holding Scripture as supreme and sufficient does not mean that all that can be known is in Scripture, but that all that is necessary for salvation and growth is provided in its formal and material aspects as a completed canon.
Which flows from the fact is that "the word of God/the Lord" was normally written, even if sometimes first being spoken, and that as written, Scripture became the transcendent supreme standard for obedience and testing and establishing truth claims as the wholly Divinely inspired and assured, Word of God. As is abundantly evidenced
And which testifies (Lk. 24:27,44; Acts 17:2,11; 18:28; 28:23, etc.) to writings of God being recognized and established as being so (essentially due to their unique and enduring heavenly qualities and attestation), and thus they materially provide for a canon of Scripture (as well as for reason, the church, etc.)
Which meant that the additional revelation of NT oral preaching was established as being of God upon Scripture substantiation in word and in power, not upon the premise of ensured perpetual magisterial infallibility. Which is the case with Rome.
Moreover, an examination of anything called "the word of God/the Lord will show it being written, or subsequently revealed, and which was wholly inspired of God, possessing a power that goes beyond merely being true. (Heb. 4;12)
Thus if God wants us to know something more than what is written, then the veracity of would have to be established upon Scripture substantiation.
In contrast the veracity of RC teaching does not rest upon that, lest she be as evangelicals, but rests upon the premise of ensured perpetual magisterial infallibility.
Nor are what she claims to pass on as traditions or any of her infallible decrees the wholly inspired words of God. Nor are even the arguments and reasoning behind them necessarily without error.
But Rome has presumed to infallibly declare she is and will be perpetually infallible whenever she speaks in accordance with her infallibly defined (scope and subject-based) formula, which renders her declaration that she is infallible, to be infallible, as well as all else she accordingly declares.
Thus a faithful RC is not to ascertain the veracity of RC teaching by examination of evidences (for that reason). For to do so would be to doubt the claims of Rome to be the assuredly infallible magisterium by which a RC obtains assurance of Truth
..in all cases the immediate motive in the mind of a Catholic for his reception of them is, not that they are proved to him by Reason or by History, but because Revelation has declared them by means of that high ecclesiastical Magisterium which is their legitimate exponent.” — John Henry Newman.
It was the charge of the Reformers that the Catholic doctrines were not primitive, and their pretension was to revert to antiquity. But the appeal to antiquity is both a treason and a heresy. It is a treason because it rejects the Divine voice of the Church at this hour, and a heresy because it denies that voice to be Divine... I may say in strict truth that the Church has no antiquity....Primitive and modern are predicates, not of truth, but of ourselves...The only Divine evidence to us of what was primitive is the witness and voice of the Church at this hour. . — Most Rev. Dr. Henry Edward Cardinal Manning, Lord Archbishop of Westminster, The Temporal Mission of the Holy Ghost: Or Reason and Revelation (New York: J.P. Kenedy & Sons, originally written 1865, reprinted with no date), pp. 227-228.
Thus the reasoning (akin to Mormonism), Catholic doctrine, as authoritatively proposed by the Church, should be held as the supreme law; for, seeing that the same God is the author both of the Sacred Books and of the doctrine committed to the Church, it is clearly impossible that any teaching can by legitimate means be extracted from the former, which shall in any respect be at variance with the latter. .(Providentissimus Deus; http://www.vatican.va/holy_father/leo_xiii/encyclicals/documents/hf_l-xiii_enc_18111893_providentissimus-deus_en.html)
And instead of being as the Bereans, implicit assent is called for,
It follows that the Church is essentially an unequal society, that is, a society comprising two categories of per sons, the Pastors and the flock...the one duty of the multitude is to allow themselves to be led, and, like a docile flock, to follow the Pastors. - VEHEMENTER NOS, an Encyclical of Pope Pius X promulgated on February 11, 1906
"The intolerance of the Church toward error, the natural position of one who is the custodian of truth, her only reasonable attitude makes her forbid her children...to endeavor to discover religious truths by examining both sides of the question. This places the Catholic in a position whereby he must stand aloof from all manner of doctrinal teaching other than that delivered by his Church through her accredited ministers." — (John H. Stapleton, Explanation of Catholic Morals, Chapters XIX, XXIII. the consistent believer (1904); Nihil Obstat. Remy Lafort, Censor Librorum. Imprimatur, John M. Farley, Archbishop of New York )
And incredibly, it is argued that one cannot even know what Scripture is with the infallible magisterium to tell him so:
"People cannot discover the contents of revelation by their unaided powers of reason and observation. They have to be told by people who have received in from on high. " - Cardinal Avery Dulles, SJ, “Magisterium: Teacher and Guardian of the Faith,” p. 72; http://triablogue.blogspot.com/2008/08/magisterial-cat-and-mouse-game.html
.the believer cannot believe in the Bible nor find in it the object of his faith until he has previously made an act of faith in the intermediary authorities between the word of God and his reading. - Catholic Encyclopedia>Tradition and Living Magisterium; http://www.newadvent.org/cathen/15006b.htm
Back to Mary and the Biblical premise of establishment of Truth based upon Scriptural substantiation, one would have a hard time in Bible times explaining kneeling before a statue and praising the entity it represented in the unseen world, and as having Divine powers and glory, and making offerings and beseeching such for Heavenly help, directly accessed by mental prayer.
Moses, put down those rocks! I was only engaging in hyper dulia, not adoring her. Can't you tell the difference?
It seems that the RC argument is that an assuredly (if conditionally) infallible magisterium is essential for determination and assurance of Truth (including writings and men being of God) and to fulfill promises of Divine presence, providence of Truth, and preservation of faith, and authority. (Jn. 14:16,26; 15:26; 16:13; Mt. 16:18; Lk. 10:16)
And that being the historical instruments and stewards of Divine revelation (oral and written) means that Rome is that assuredly infallible magisterium. Thus any who knowingly dissent from the latter must be in rebellion to God. Does this fairly represent what you hold to or in what way does it differ?