Luther set up his own conscience as his standard for Christianity. Whether Luther intended to or not, the end result was that his own personal interpretation of Scripture became his standard. While Calvin and other subsequent reformers cited the ECF as pursuasive authority, Protestantism (largely because of Luther) evolved to the point of Alexander Campbell's argument that all he needed to do was read the Bible with fresh eyes, with absolutely no deference to creeds, councils, or traditions. Alexander Campbell is hardly extreme in Protestantism today - indeed, I would argue that he is mainstream (much to my own dismay). His argument is rooted in the alleged perspecuity of the Scriptures - that the Bible is supposedly completely clear. As a Presbyterian who adheres to the Westminster standards, I do not believe in complete perspecuity, but only that "all things pertaining to salvation" are clear.
Luther, to the extent that he set himself up as his own (perhaps not final, but his own) arbitrator as the meaning of the Scriptures (and, indeed, what the Scriptures were - throwing out James - and almost Revelation - was incomprehensible, and should disqualify him from ever being cited as any sort of authority. His stand against the abuses of indulgences was noble, as even Campion might concede, but his sheer hubris in thinking he had the right to exclude a book from the New Testament set himself up as his own Magisterium.
If it were not for Luther you would not have your Westminster Standards. Also the Westminster Standards have been modified since they were originally promulgated, have they not? Under what authority were they modified? Indeed, under what authority were they promulgated?
If the drafters of the Westminster Confession or (Calvin or Luther) were not led by the Holy Spirit, then they had no authority whatsoever to set down any standards. They might as well have just closed their minds and bowed to the Pope.
Even I [gasp] would concede that his stand against the abuses of indulgences (though not against indulgences themselves) was noble. ;-)
And there are plenty of legitimately orthodox Catholics who would agree with me; Peter Kreeft for one. I daresay the Pope would be another.
I would disagree that Luther relied solely upon his own personal interpretation of Scripture. Certainly his viewpoints were colored by the teachings from the Church fathers for he brought some of the Catholic teachings (e.g. infant baptism, Mary’s perpetual virginity) from the Roman Catholic Church. It's hard to believe Luther didn’t look back into many of these writings for guidance as well to ensure his interpretations were correct. After all, his eternal soul rested upon his accuracy. (BTW-Luther wasn’t the only one doing this during this time (e.g. Wycliffe, Hus)). The only difference between Luther and the Catholics was that Luther made his anchor the word of God instead of the “overall” Church interpretation.
John Calvin was the person responsible for putting together the Protestant’s theology. This wasn’t pulled out of the sky based solely upon scripture and personal interpretation. There was obviously much work based upon the writings of the church fathers as well as scripture. Calvin quotes liberally from these men. I came to the conclusion that John Calvin was correct not by reading his works but by reading the works of Augustine and many of the early western church fathers.
Heretics and heretical doctrines come in many sizes and shapes. Most of the early Protestant heretics such as Campbell came out of the Protestant Reformed churches just like Pelagius came out of the Roman Catholic Church. To state Luther as the cause for Campbell is as wrong as saying Luther was responsible for Joseph Smith.