There are many Christians today who imagine that it is unloving and un-Christian to engage in polemics. Polemics are theological warfare, the practice of opposing, exposing and refuting false teaching.
There are other who imagine that heretics and heresies no longer exist. Heretics, false brethren, false teachers, deceivers and false gospels are only theoretical. This would mean that after centuries of struggle with false doctrine the church can relax. No new threats are on the horizon. The warnings of apostasy can be safely ignored.
Others believe that it is wrong to name false teachers.
None of these views is biblical. The minister has the calling to oppose lies out of the love of the truth. Below is a survey of the New Testament. Other passages could be added.
PROOF THAT CHRIST AND HIS APOSTLES OPPOSED, EXPOSED AND REFUTED FALSE DOCTRINE AND FALSE TEACHERS
Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves … Then understood they how that he bade them not beware of the leaven of bread, but of the doctrine of the Pharisees and of the Sadducees … And Jesus answered and said unto them, Take heed that no man deceive you. For many shall come in my name, saying, I am Christ; and shall deceive many … And many false prophets shall rise, and shall deceive many … For there shall arise false Christs, and false prophets, and shall shew great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect (Matt 7:15; 16:6; 24:4-5, 11, 24).
Woe unto you, when all men shall speak well of you! for so did their fathers to the false prophets (Luke 6:26).
Ye stiffnecked and uncircumcised in heart and ears, ye do always resist the Holy Ghost: as your fathers did, so do ye. Which of the prophets have not your fathers persecuted? and they have slain them which shewed before of the coming of the Just One; of whom ye have been now the betrayers and murderers … O full of all subtlety and all mischief, thou child of the devil, thou enemy of all righteousness, wilt thou not cease to pervert the right ways of the Lord? … For I know this, that after my departing shall grievous wolves enter in among you, not sparing the flock. Also of your own selves shall men arise, speaking perverse things, to draw away disciples after them. Therefore watch, and remember, that by the space of three years I ceased not to warn every one night and day with tears (Acts 7:51-52; 13:10; 20:29-31).
Would to God ye could bear with me a little in my folly: and indeed bear with me. For I am jealous over you with godly jealousy: for I have espoused you to one husband, that I may present you as a chaste virgin to Christ. But I fear, lest by any means, as the serpent beguiled Eve through his subtlety, so your minds should be corrupted from the simplicity that is in Christ. For if he that cometh preacheth another Jesus, whom we have not preached, or if ye receive another spirit, which ye have not received, or another gospel, which ye have not accepted, ye might well bear with him. For such are false apostles, deceitful workers, transforming themselves into the apostles of Christ. And no marvel; for Satan himself is transformed into an angel of light. Therefore it is no great thing if his ministers also be transformed as the ministers of righteousness; whose end shall be according to their works (II Cor. 11:1-4, 13-15).
But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed. As we said before, so say I now again, If any man preach any other gospel unto you than that ye have received, let him be accursed … And that because of false brethren unawares brought in, who came in privily to spy out our liberty which we have in Christ Jesus, that they might bring us into bondage, to whom we gave place by subjection, no, not for an hour; that the truth of the gospel might continue with you … But when Peter was come to Antioch, I withstood him to the face, because he was to be blamed … But when I saw that they walked not uprightly according to the truth of the gospel, I said unto Peter before them all, If thou, being a Jew, livest after the manner of Gentiles, and not as do the Jews, why compellest thou the Gentiles to live as do the Jews? … O foolish Galatians, who hath bewitched you, that ye should not obey the truth, before whose eyes Jesus Christ hath been evidently set forth, crucified among you … Ye did run well; who did hinder you that ye should not obey the truth? This persuasion cometh not of him that calleth you. A little leaven leaveneth the whole lump … I would they were even cut off which trouble you (Gal 1:8-9; 2:4-5, 11, 14; 3:1; 5:7-9, 12).
That we henceforth be no more children, tossed to and fro, and carried about with every wind of doctrine, by the sleight of men, and cunning craftiness, whereby they lie in wait to deceive (Eph 4:14)
Beware of dogs, beware of evil workers, beware of the concision … For many walk, of whom I have told you often, and now tell you even weeping, that they are the enemies of the cross of Christ (Phil 3:2, 18)
I say, lest any man should beguile you with enticing words … Beware lest any man spoil you through philosophy & vain deceit, after the tradition of men, after the rudiments of the world, and not after Christ (Col 2:4, 8).
And for this cause God shall send them strong delusion, that they should believe a lie that they all might be damned who believed not the truth, but had pleasure in unrighteousness (II. Thess. 2:11-12).
Them that sin rebuke before all, that others also may fear … If any man teach otherwise, and consent not to wholesome words, even the words of our Lord Jesus Christ, and to the doctrine which is according to godliness, he is proud, knowing nothing, but doting about questions and strifes of words, whereof cometh envy, strife, railings, evil surmising, perverse disputings of men of corrupt minds, and destitute of the truth, supposing that gain is godliness: from such withdraw thyself … O Timothy, keep that which is committed to thy trust, avoiding profane and vain babblings, and oppositions of science falsely so called, which some professing have erred concerning the faith (I. Tim. 5:20; 6:3-5, 20).
But shun profane and vain babblings: for they will increase unto more ungodliness. And their word will eat as doth a canker: of whom is Hymenaeus and Philetus, who concerning the truth have erred, saying that the resurrection is past already; and overthrow the faith of some … Preach the word; be instant in season, out of season; reprove, rebuke, exhort with all longsuffering and doctrine (II. Tim. 2:16-18; 4:2).
Holding fast the faithful word as he hath been taught, that he may be able by sound doctrine both to exhort and to convince the gainsayers. For there are many unruly and vain talkers and deceivers, specially they of the circumcision whose mouths must be stopped, who subvert whole houses, teaching things which they ought not, for filthy lucre's sake. One of themselves, even a prophet of their own, said, The Cretians are always liars, evil beasts, slow bellies. This witness is true. Wherefore rebuke them sharply, that they may be sound in the faith … These things speak, and exhort, and rebuke with all authority. Let no man despise thee … A man that is an heretic after the first and second admonition reject, knowing that he that is such is subverted, and sinneth, being condemned of himself (Tit 1:9; 2:15; 3:10-11).
But there were false prophets also among the people, even as there shall be false teachers among you, who privily shall bring in damnable heresies, even denying the Lord that bought them, and bring upon themselves swift destruction. And many shall follow their pernicious ways; by reason of whom the way of truth shall be evil spoken of. And through covetousness shall they with feigned words make merchandise of you: whose judgment now of a long time lingereth not, and their damnation slumbereth not (II. Pet 2:1-3).
Who is a liar but he that denieth that Jesus is the Christ? He is antichrist, that denieth the Father and the Son … Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world. Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God. And every spirit that confesseth not that Jesus Christ is come in the flesh is not of God: and this is that spirit of antichrist, whereof ye have heard that it should come; and even now already is it in the world (I. John 2:22; 4:1-3)
Whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son. If there come any unto you, and bring not this doctrine, receive him not into your house, neither bid him God speed: For he that biddeth him God speed is partaker of his evil deeds (II John 9-11).
I wrote unto the church: but Diotrephes, who loveth to have the preeminence among them, receiveth us not. Wherefore, if I come, I will remember his deeds which he doeth, prating against us with malicious words: and not content therewith, neither doth he himself receive the brethren, and forbiddeth them that would, and casteth them out of the church (III. John 9-10).
Beloved, when I gave all diligence to write unto you of the common salvation, it was needful for me to write unto you, and exhort you that ye should earnestly contend for the faith which was once delivered unto the saints (Jude 3).
But this thou hast, that thou hatest the deeds of the Nicolaitans, which I also hate … But I have a few things against thee, because thou hast there them that hold the doctrine of Balaam, who taught Balac to cast a stumblingblock before the children of Israel, to eat things sacrificed unto idols, and to commit fornication … Notwithstanding I have a few things against thee, because thou sufferest that woman Jezebel, which calleth herself a prophetess, to teach and to seduce my servants to commit fornication, and to eat things sacrificed unto idols (Rev 2:6, 14, 20)
PROOF THAT THE REFORMED MINISTER IN PARTICULAR MUST OPPOSE FALSE DOCTRINE TO BE FAITHFUL TO HIS ORDINATION VOW AND MUST NOT ONLY BE A "POSITIVE PREACHER"
“We declare, moreover, that we not only reject all errors that militate against this doctrine and particularly those which were condemned by the above mentioned synod [Dordt, 1618-1619], but that we are disposed to refute and contradict these, and to exert ourselves in keeping the church free from such errors” … “That they faithfully explain to their flock, the Word of the Lord, revealed by the writings of the prophets and the apostles; and apply the same as well in general as in particular, to the edification of the hearers; instructing, admonishing, comforting and reproving, according to every one's need; preaching repentance towards God, and reconciliation with him through faith in Christ; and refuting with the Holy Scriptures, all schisms and heresies which are repugnant to the pure doctrine” … “To ward off false doctrines and errors that multiply exceedingly through heretical writings, the ministers and elders shall use the means of teaching, of refutation, or warning, and of admonition, as well in the ministry of the Word as in Christian teaching and family-visiting”(Formula of Subscription; Form for the Ordination of the Ministers of God’s Word; Church Order [Art. 55]).