A quick way to Stump Catholics who Oppose the Great Apostasy

I have recently encountered (mainly on facebook groups I lurk) an on-going debate between Latter-day Saints and Roman Catholics vis-a-vis the Great Apostasy and Rome's claims to be the one true Church. Beyond the realm of biblical proof-texting (not that I do not think such is important), let us boil down why Rome is a false Church and is apostate (not that "Mormonism" is true--that is a different issue).

(1): According to Roman Catholicism, her dogmas are apostolic in origin, preserved in the written word (the Bible) and/or oral teachings from Jesus and/or the apostles themselves ("apostolic [oral] tradition"):

That Revelation was given in its entirety to Our Lord and His Apostles. After the death of the last of the twelve it could receive no increment. It was, as the Church calls it, a deposit — "the faith once delivered to the saints" (Jude, 2) — for which the Church was to "contend" but to which she could add nothing. Thus, whenever there has been question of defining a doctrine, whether at Nicæa, at Trent, or at the Vatican, the sole point of debate has been as to whether the doctrine is found in Scripture or in Apostolic tradition.  (Catholic Encyclopedia, "Revelation")

(2): If Rome were to proclaim, as dogma, something that was not apostolic in origin, it is not preaching the truth as it destroys her claim to infallibility.

(3) If Rome were to be guilty of no. 2, it is not the true Church, even by her own claims.

Are there beliefs, proclaimed as dogmas that are not apostolic in origin? Yes. Here are two:

The Immaculate Conception of Mary

The Veneration of Images/Icons

To put it succinctly:

(1) According to Rome, as they are defined dogmas, proclaimed as such by the infallible teaching authority of the Church, the Immaculate Conception of Mary (dogmatically defined in 1854) and the veneration of images (defined at Second Nicea [787]) are apostolic traditions

(2) However, the Immaculate Conception of Mary and the veneration of images are not apostolic in origin, but man-made traditions (see the articles above)

(3) The conclusion drawn is Rome is false and apostate, as she has proclaimed beliefs to be de fide dogmas which are, in reality, false, man-man traditions, thus also showing her claims to infallibility is false.

Any Catholic apologist who takes exception to this is more than welcome to show me the apostolic witness of the Immaculate Conception and/or veneration of images. Until then, one is, in terms of the Great Apostasy debate, justified in rejecting Roman Catholic truth claims.