Again, you quote Vincent of Lerins incorrectly. Or rather, the sources who gave you that, quote him incorrectly and out of context. This was not a diatribe against the IC rather a statement against Pelagianism.
You just don't get it. You can't believe there was even so much as ONE sinless person (including Mary) without embracing pelagianism. Since we know there is indeed the doctrine of ORIGINAL SIN, there CANNOT be even ONE person exempted. PERIOD. When your sainted magisterium lays claim to that ONE person named Mary who was suddenly conceived WITHOUT SIN, then you have denied the time honored dogma of original sin. By doing so you have embraced heresy.
There is absolutely NO Scriptural support for Mary's immaculate conception. Even you Catholics admit this from the Catholic Encylopdia. Key phrase: "No direct or categorical and stringent proof of the dogma can be brought forward from Scripture."
The only vague Scripture you twist to try and show some scriptural support for this heretical dogma is Luke 1:28. But "full of grace" in that passage can not possibly mean conceived without sin, for the very same word is used in Ephesians 1:6 referring to ALL believers.
Contrary to the Roman Catholic teaching, Scripture plainly teaches that all Adam's descendents share his sinful nature: "Therefore, just as through one man sin entered the world, and death through sin, and thus death spread to all men, because all sinned" (Romans 5:12). Therefore all Adam's children need to be saved. Mary herself, a natural descendant of Adam, calls God "my savior" (Luke 1:47). Evidently she did not know the Roman Catholic doctrine of the Immaculate Conception!
It is Christ alone, the eternal Son who was supernaturally conceived by the Holy Spirit in the womb of the virgin woman, it is ever expressly stated that He was "without sin" (Hebrews 4:15). Christ alone is immaculate from conception; therefore He alone is qualified to die in the place of sinners. Christ, who knew no sin, "bore our sins in His own body on the tree" (1 Peter 2:24).
Take the blinders off. The unbiblical dogmas taught by the RCC supplant Christ, they deny Him His glory, His majesty, His power, and His saving work on the Cross. They are HERESY and have been heresy since the 5th century when such ideas were FIRST introduced!!