Now before you get upset, the point I am about to make is not my own opinion but one I regularly hear. How do you know that the interpretation you have been given is the correct one? How can *you *be sure that what you have been taught is true? Many non Catholic Christians use Scripture to discern if the teaching they receive is correct. As Scripture is the Word of God and therefore cannot lie, anything which disagrees with Scripture must be incorrect.
Certain Catholic teachings do seem to disagree with Scripture. For example, the apostles did not exalt themselves above the lay people the way the Magisterium does. So if this disagrees with Scripture then it should be deemed incorrect but the Church is allowed to (theoretically) say theu know better than Scripture.