Every argument needs to build on recognized truths. When your initial premise seeks to build upon the falsehood that Catholics are not among "Bible believing Christians" there can be no acceptable proof of your thesis.
If you begin with a premise that the Catholic Church teaches a different interpretation of the Bible than your particular flavor of non-Catholic then we can build upon.
By the way, your link is a discussion of Justification, not Grace. As for differentiating Catholics from so-called "Bible believing Christians" would you care to expand upon the differences in the doctrines related to grace and justification between Luther, Calvin, Zwingli, Wesley, Knox, Arminius, Murray and Swedenborg.
Peace be with you.
The term "Bible believing Christians" is certainly not a descriptor I made up. It is well recognized and widely, widely used. Almost universally.
At the very heart of this debate is God's word. That is what should be the authority. Period.
I certainly did not invent this "premise" that the Catholic church either ignores or misinterprets scripture vis a vis its doctrine. I could start at the Reformation and move from there.