Here is one of the things that C.F.W. Walther, the first president of the LCMS, says about pure doctrine back on September 11, 1885 from one of his lectures in his best-known work, "The Proper Distinction Between Law and Gospel." It seems as though some things haven't changed in at least 100 years:
Nowadays any one who insists that pure doctrine is a very important matter is at once suspected of not having the right Christian spirit. The very term "pure doctrine" has been proscribed and outlawed. Even such modern theologians as wish to be numbered with the confessionalists, as a rule, speak of pure doctrine only in derisive terms, treating it as the shibboleth of dead-letter theology. If any one goes to the extreme, as it is held to be, of even fighting for the pure doctrine and opposing every false doctrine, he is set down as a heartless and unloving fanatic. What may be the reason? Unquestionably this, that modern theologians know full well that they have not that doctrine which in all ages has been called, and verily is, the pure doctrine. Furthermore, they even think that pure doctrine does not exist (is a non-ens), except in a dream-world, in the realm of ideals, in the Republic of Plato.
The time in which we live is that to which the apostle refers when he says of errorists that they are "ever learning and never able to come to the knowledge of the truth." 2 Tim. 3, 7.
The spirit of our time is that of Pilate, to whom the Lord had testified that He was a King of Truth in a kingdom of truth, and who sneeringly replied, "What is truth?" John 18, 38. This unhappy man was most likely thinking in his heart that, since the greatest minds for thousands of years had vainly tried to find the answer to the question, What is truth? this poor beggar, this contemptible Nazarene, Christ, made Himself simply ridiculous with His claim that He was the King of Truth and would establish a kingdom of incontrovertible and eternal truth.
Contempt of the pure doctrine is contempt of the truth; for the pure doctrine is simply nothing else, absolutely nothing else, than the pure Word of God. It is not, as some think, the doctrine adapted to the systems of dogmaticians that has been accepted by the Church. Accordingly, contempt of the pure doctrine is proof that we are living in an unspeakably lamentable era. For listen in what terms the Scriptures themselves speak of God's Word and the pure doctrine. In the prophecies of Jeremiah we read, chap. 23, 28: "The prophet that bath a dream, let him tell a dream; and lie that bath My Word, let him speak My Word faithfully. What is the chaff to the wheat? saith the Lord."
David addresses God Himself in these words of Ps. 94, 20: "Shall the throne of iniquity have fellowship with Thee, which frameth mischief by a law?" By the term "law" he refers, in general, to the Word of God. What says our dear Lord Christ Himself regarding this matter? In John 8, 31. 32 He says: "If ye continue in My Word, then are ye My disciples indeed; and ye shall know the truth, and the truth shall make you free."
Over against this, German theologians are not ashamed to say: "Bah! We are seeking after truth, but only a conceited, self-satisfied person will claim to have achieved it." Such talk shows to what depths we have sunk. Does not the Lord say distinctly: "Ye shall know the truth, and the truth shall make you free"? Jude, the faithful apostle, writes in his epistle, v. 3: "Beloved, when I gave all diligence to write unto you of the common salvation, it was needful for me to write unto you that ye should earnestly contend for the faith which was once delivered unto the saints." The apostle is referring, not to faith in a person's heart, but to faith objectively viewed, that is, to the pure doctrine.