Frankly, what I'm about to write is hilarious considering that on this thread there are Catholics arguing over the degree of assent one must give to the teaching of JPII and whether the BVM is the co-redemptrix and/or the mediatrix of all Graces, but such is life.
People who listen to the quiet voice inside, open their Bibles and search for themselves come up with opposing views that are fundamental and quite incompatible. Some will tell us that Jesus Christ is God, others will tell us that He was created and therefore not God. Some will claim that there is no Trinity, others that there is a Trinity. Some people claim that once one is saved there is nothing that can separate a person from God, others will assert that salvation can be lost. Some claim that Baptism is regenerative, others say not. That's just off the top of my head based on threads I've seen recently right here in the religion forum. All of them will base their beliefs on a right interpretation of Sacred Scripture and the personal guidance of the Holy Ghost.
What I find particularly fascinating is that most of the people who hold such diametrically opposing views will ignore them whenever they share a disagreement with Catholic doctrine. People who disagree on whether Jesus Christ is God will ignore what is truly the most important question anyone can answer if they can attack Catholicism for what the Church teaches about Mary, or any distinctively Catholic belief.