But I have seen many Protestants cast doubts upon the Word of God

Calvino:

Yep, they are willing to shamelessly cast doubt on God's word all for the same of trying to give glory to their denom. It is sad.

I have yet to see even one Catholic cast doubt upon God's Word. Beginning with Luther, I have seen many Protestants who disparage the Scriptures.  Many Protestants today say:

Mark 16:16 is not part of the Bible.
1 John 5:6 is not part of the Bible.

And all of them cast out the Deuterocanonicals.

This is in line with Luther's attitude toward Scripture.  He said:

I am so hostile to this book and to Esther that I could wish they did not exist at all; for they judaize too greatly and have much pagan impropriety.” ( Tischedren, I, Weimar Edition, 1912, 208)

He even wanted to discard five books of the New Testament, chief amongst them the Epistle of St. James which he called the Epistle of straw.

Sincerely,

De Maria