1. Scripture alone is infallible.
2. Therefore Sacred Tradition can't be infallible.

The Catholic position is this.

1. Where does Scripture say that Scripture ALONE is infallible? We don't see it.
2. Sacred Tradition was the source of Sacred Scripture, therefore it must have also been infallible at least before Scripture was written.
3. Holy men spoke the Traditions and wrote the Scriptures, therefore, they must have been infallible also.
4. Those holy men all belonged to the same Church, therefore the Church must have been infallible also.
5. Neither Scripture nor Tradition nor the Church, ever state that Tradition or the Church somehow lost the charism of infallibility.

Lets break it down.

Jesus Christ is infallible. He taught His disciples infallibly and left them to teach as He taught.

The Catholic presumption is that He left them to teach infallibly. I assume that Catholics and Protestants agree that the Apostles and disciples passed down the Traditions of Jesus Christ infallibly.

Just in case some Protestant's don't agree, here's what Scripture says on the matter:
2 Peter 1:19-21

King James Version (KJV)
19We have also a more sure word of prophecy; whereunto ye do well that ye take heed, as unto a light that shineth in a dark place, until the day dawn, and the day star arise in your hearts:
20Knowing this first, that no prophecy of the scripture is of any private interpretation.
21For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost.
So, if the Holy Spirit inspired the men to write infallibly, why not to teach infallibly?Notice that holy men were not only moved by the Holy Spirit to write, but also to preach. That verse seems to indicate then, that:

1. Holy men spoke infallibly (moved by the Holy Ghost).
2. Holy men wrote infallibly (also moved by the Holy Ghost).

There are more verses which show that Sacred Tradition is infallible at the time of the Apostles.
Hebrews 13:7
Remember them which have the rule over you, who have spoken unto you the word of God: whose faith follow, considering the end of their conversation.

If the word of God is infallible, then the Traditions passed down by these men was infallible.

Romans 10:17

King James Version (KJV)
17So then faith cometh by hearing, and hearing by the word of God.

Not reading the word of God.

1 Thessalonians 2:13

King James Version (KJV)
13For 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.

All these show that the word of God was taught by word and also shows that Scripture expects that to be the case. There is no indication anywhere that either the Church or Tradition will lose their infallibility at a certain point in time.
Let me know what you think.

Sincerely,

De Maria