Protestants believe the Holy Spirit cannot and did not protect Scripture from including errors for roughly eighteen hundred years. They also believe that neither Jesus Christ or the Apostles thought Scripture was important enough to mention the fact the the same Jews they took to task for so much else had also included books in in the Septuagint that shouldn't be there.
Catholics believe the Holy Spirit can and does protect Scripture from the inclusion of error including when the Septuagint was put together. Furthermore, Catholics believe that Christ and the Apostles held the Scriptures dear enough that they would have made it clear errors had been included in the Septuagint if that was in fact the case.
It boils down to Catholics trusting in the Holy Spirit to safeguard His Word while Protestants prefer to trust in anti-Christ, anti-Christian, Pharisees.
Actually, you have this backwards.
As a Christian I believe the Bible, and only the Bible, is God breathed. Not catholic tradition. It is the Holy Spirit which has given us the Word....not the catholic church. It is the Word we are to look to, as the apostles did, for guidance....not tradition.
It is the catholic church which has elevated Mary to her position of almost equaling Christ in the role of salvation. "Mary is the intermediary through whom is distributed unto us this immense treasure of mercies gathered by God, for mercy and truth were created by Jesus Christ. Thus as no man goeth to the Father but by the Son, so no man goeth to Christ but by His Mother." (Vatican Website: Encyclical of Pope Leo 13th on the Rosary, Octobri Mense, Pope Leo 13th, 1903-1914)
The catholic church teaches its members to pray to mary.
It is the catholic church that teaches that Mary was sinless in contradiction of Romans 3:23 "for all have sinned and fall short of the glory of God."
It is the catholic church that teaches its members that Mary was remained virgin in spite of the clear teaching of the Bible that Jesus had step-brothers and sisters.
It is the catholic church that has established the papacy and the title of pope...neither is supported by the Bible.
I could go on about indulgences, penance, working for your salvation, etc, but I think you get the idea.