Walther to Philip Schaff: "This you do not teach!" (What?)

Who followed Franz Pieper as president of Concordia Seminary when he died?  Ludwig Fuerbringer.  And Fuerbringer wrote a book in his later years of his remembrances, calling it 80 Eventful Years; Reminiscences of Ludwig Ernest Fuerbringer.  I have spoken before about President Fuerbringer and the sad fall of the Missouri Synod during his tenure.  But in his "reminiscences", he reported the following about C.F.W. Walther and a certain well-known church historian (pages 87-88):

Walther was very interesting when he had guests at his table. ... I remember that one day Dr. Philip Schaff, the well-known church historian and Re­formed theologian and founder of the American Society of Church History, at that time professor in Union Theological Seminary in New York, called on him. At the close of his [page 88] visit Walther showed him through our new Seminary build­ing, and I had occasion to note that the conversation was quite animated. But also on such occasions Walther never failed to testify. I do not know what was under discussion, but I heard Walther say very emphatically: “Das lehren Sie eben nicht,” this you do not teach. And finally I saw that he escorted Dr. Schaff to the streetcar and very courte­ously bade him adieu. 

Philip Schaff

As one reads Fuerbringer's account of Walther's exchange with Dr. Philip Schaff, it is quite apparent that Walther, through all his courteous manner, was quite forceful with the unionistic Dr. Schaff.  But what was it that Walther was referring to when he spoke the following words to the widely known "Church Historian" Philip Schaff:

"This you do not teach!"

What was it that Walther charged the great Schaff, the writer of 8 volumes of Church History, with NOT teaching?  Although Ludwig Fuerbringer could not tell us, I will tell you, dear reader.  It was this:

The Lutheran Doctrine of Justification

 That is what all the Reformed DO NOT TEACH ==>> the pure, unconditional Gospel!

= = = = = = = = = = = = = = = = = = = = = = = = 

What does this mean?  It means that all the "Church History", all 8 volumes of Schaff's massive work is suspect in its spiritual judgments.  It means that Dr. Philip Schaff is NOT the best source of "Church History" because, as C.F.W. Walther put it to him, "This you do not teach".

And so all true Lutherans should bid "adieu" to the Reformed saying "You left your first love, the love of the Lutheran Church – the pure, unconditional Gospel... this you do not teach"