That, and all the other such statements are fallacious, except in cults and in Rome, in which both basically hold an individual as having assuredly veracity.
Likewise fallacious is the premise that holding Scripture as supreme is unscriptural while holding the pope and church as supreme is, and produces a superior Scriptural unity.
And that holding Scripture as supreme as the accurate wholly inspired and supreme authority does not produce fruit of superior conservative unity than the fruit of the Roman model, as while Scripture does not change, leadership can, and to which the laity look for interpretation, and faith is shown by what we do.
And that the one true church is the visible one, only consisting of members of the body of Christ.
Is your 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?
And that being the historical instruments and stewards of Divine revelation (oral and written) means that such is that assuredly infallible magisterium, dissent from which invalidates one form having authority?
And that the Roman model precludes the church being one in which there was an almost entire abandonment of equity in ecclesiastical judgments, and severely lacking discipline in morals, and erudition in sacred literature, and reverence in divine things, so that true religion was almost extinct, so that the true Church had to be sought outside the institution.
Answer me.
Don't hold your breath... ; )