Well, Luther asserted that the deuterocanonical books were apocrypha that were not originally part of the scripture. He had been deceived by their absence from the Jewish scriptures of his day. For a Protestant acknowledgment that the deuterocanonical books were part of a Pre-Christian canon, see here: http://www.britannica.com/eb/article-73165 (Qumran)
For acknowledgment that the Alexandrian canon -- the one universally read by Hellenic Jews at the time of Christ -- included "additional chapters" of Daniel and Esther, see here: http://www.britannica.com/eb/article-73164
Or here, describing how the post-Christian Council of Jamnia is where the Jews first rejected the deuterocanonicals, in 70 AD: http://biblescripture.net/Canon.html
Given that we KNOW for certainty that Luther was wrong, I can't BEGIN to tell you how the "Reformers" justify excluding the deuterocanonicals.
But this is just wierd:
Luther and the Reformers claim "sola scriptura": If it isn't in the bible, it's a false doctrine. (Of course sola scriptura isn't in the bible.)
But at the Diet of Worms, the Catholic Church convincingly proved to Luther that the doctrines he so detested actually WERE in scripture.
Luther then reasoned that if what SEEMED to be scripture contained doctrines he hated, it couldn't possibly be true scripture. Seizing apon the fact that the Jews didn't consider many of hte most problemmatic books to be scripture, Luther used that as a justification that they weren't scripture. (Of course, he was unbothered by the fact that the Jews accepted NONE of the New TEstament...)
But Luther was ignorant of two matters. 1. There were other defenses of the doctrines he hated in the bible; the Diet of Worms merely stated some of the easiest defenses. 2. The books WERE, in fact, treated as scripture by Jews until the Council of Jamnia in 70 AD.
At this time, the assertion that the deuterocanonicals had ever, at any time, been considered non-scriptural by any orthodox Christian* at any time prior to Luther is so strongly refuted that the assertion constitues an outright deliberate lie by any knowledgeable person who repeats it, but unfortunate the lie is so pervasive in American society, it is cited as fact in many of the very same reference books which include the positive debunking of the fact, including the Oxford Biblical Commentary, the Encyclopaedia Brittanica, etc. Hence, it is commonly repeated as "common knowledge" by many people who plainly acknowledge its falseness!
(*By orthodox Christian, I mean only to exclude Judaizers and those who sought to exclude all traces of Judaism from Christianity, such as the Manicheans.)
As I am sure you are aware, the Apocrypha was not first disputed by Luther. Jerome disputed it in the fifth century. The Catholic church itself did not declare the books canonical until the Council of Trent in 1546. Both Luther (http://www.jesus-is-lord.com/apocryph.htm) and Jerome (http://www.justforcatholics.org/a108.htm) considered them "good reading", but not authoritative.
Luther and the Reformers claim "sola scriptura": If it isn't in the bible, it's a false doctrine. (Of course sola scriptura isn't in the bible.)
I believe you have misrepresented sola scriptura. I think it is better boiled down to (and, remember, definitions of sola scriptura are not universal) "the Bible alone is inerrant." This is opposed to the teaching of the Catholic church, which declares that the pope, when acting in the capacity of his office, makes a declaration it is also inerrant (divinely inspired).
Or, as A.A. Hodge put it, "Whatever God teaches or commands is of sovereign authority. Whatever conveys to us an infallible knowledge of his teachings and commands is an infallible rule. The Scriptures of the Old and New Testaments are the only organs through which, during the present dispensation, God conveys to us a knowledge of his will about what we are to believe concerning himself, and what duties he requires of us." This does not equate to "whatever not found in the Bible is false."
I contend that the Bible alone is inerrant. There are things that are true that are not found in the Bible, but nothing is true that contradicts it (and the Catholic Church has contradicted it).
Martin Luther was a godly man (though by no means inerrant) who has done much good for the Kingdom of God and, in doing so, changed the course of history. I am tired of hearing him bashed.
The Jews were guilty of adding to the Scriptures even if you discount the Apocrypha. Jesus denounced the Pharisees for this (Matthew 15:3-9). As for not being able to understand why Protestants reject the Apocrypha, the typical reasons I know are on this page: http://www.jesus-is-lord.com/apocryph.htm. For this page I offer one note: the author states that Catholics are not Christians. I would counter that anyone who believes everything the Catholic church teaches is not a Christian, but that there are Christians in the Catholic church. If you looked at my FR homepage, you know one of my favorite authors is GK Chesterton--a Catholic.
The finding of Tobias, Sirach, Letter of Jeremiah, and Psalm 151 at Qumran answer only the first objection and only for those books.
Which of Luther's teachings were proven false through Scripture at Worms and what were the arguments used to refute them? The Exsurge Domine does not refute anything. It just makes forty-one declarations.
The Catholics themselves have rejected books from the Septuagint. III Macabees, I Esdras, and the Prayer of Manasseh. Why did the Roman Church reject those as non-canonical?
Whatever you hold, there is one fundamental aspect to this whole thing to keep in mind: acceptance of a canon (by anyone in any religion) is a matter of faith. No Christian can ever prove that any set of books is the word of God, but by the Holy Spirit working in us we can sense truth, are convicted of our crime and are brought before the cross to confess our sins and be cleansed in the fiery river of Jesus's blood spilled for us that whoseoever believes may have life and have it to the fullest. Whatever else we may agree or disagree on, let us agree on these (no, I am not shying from the discussion at hand; as humans it is always good for us to remember the broader picture):
"For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life. For God did not send his Son into the world to condemn the world, but to save the world through him. Whoever believes in him is not condemned, but whoever does not believe stands condemned already because he has not believed in the name of God's one and only Son." John 3:16-18
"If anyone does not love the Lord—a curse be on him. Come, O Lord! The grace of the Lord Jesus be with you." 1 Corinthians 16:22-23