Christians should oppose those who deny the doctrines of imputation

"In these days of boasted liberality, it may appear captious to oppose with zeal the errors of men who have acquired a name in the Christian world. The mantle of charity, it will be said, ought to be thrown over mistakes that have resulted from a free and impartial investigation of truth, and if not wholly overlooked, they should be noticed with a slight expression of disapprobation. Such, however, was not the conduct of the Apostle Paul. He spared neither churches nor individuals, when the doctrines they maintained tended to the subversion of the Gospel; and the zeal with which he resisted their errors was not inferior to that with which he encountered the open enemies of Christianity. He affirms that the doctrine introduced into the Galatian churches is another Gospel, and twice pronounces a curse against all by whom it was promulgated. Instead of complimenting the authors of this corruption of the Gospel as only abusing in a slight degree the liberty of free examination, he decides that they should be cut off as troublers of the churches. Let not Christians be more courteous in expressing their views of the guilt and danger of corrupting the Gospel, than faithful and compassionate to the people of Christ who may be injured by false doctrine. It is highly sinful to bandy compliments at the expense of truth.

The awful responsibility of being accessory to the propagation of error is strongly expressed by the Apostle John. '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.’ If the imputation of Adam's sin and of Christ’s righteousness be doctrines contained in the word of God, commentaries that labour to expel them from that word must be grossly pestiferous books, which no Christian ought to recommend, but which, on the contrary, to the utmost of his power, it is his duty to oppose."

Robert Haldane, "Commentary on Romans"

 

“Dr. Macknight has a long note on this verse, which is also directly opposed to the Apostle’s doctrine of justification, ‘In judging Abraham,’ he says, ‘God will place on the one side of the account his duties, and on the other his performances. And on the side of his performances he will place his faith, and by mere favour will value it as equal to a complete performance of his duties, and reward him as if he were a righteous person. But neither here, nor in Gal. iii. 6, is it said that Christ’s righteousness was counted to Abraham. In both passages the expression is, Abraham believed God, and it, viz., his believing God, was counted to him for righteousness. Further, as it is nowhere said in Scripture that Christ's righteousness was imputed to Abraham, so neither is it said anywhere that Christ’s righteousness is imputed to believers.’ These statements, affirming that God, in judging Abraham, will place on the one side of the account his duties, and on the other his performances, and by mere favour will value faith as equal to a complete performance of his duties, argue most deplorable ignorance of the whole plan of salvation. The assertion, that it is nowhere said in Scripture that Christ’s righteousness is imputed to believers, is directly contrary to fact. It is contradicted by the whole strain of Scripture relating to the subject, and expressly by the Apostle Peter, in his address to them that have obtained like precious faith with us, in the righteousness of our God and Saviour Jesus Christ, 2 Pet. i. 1, (This is the literal rendering.) And also by the Prophet Jeremiah, xxiii. 6, by whom Jesus Christ is called the Lord our righteousness. But by such groundless assertions does Dr. Macknight misrepresent the character of God, and labours to banish from the Bible the doctrine of the imputation of Christ’s righteousness, without which, consistently with the perfections of God and the demands of the law, there could be no salvation. He misunderstands, too, the meaning of the expression, for righteousness.”

- Robert Haldane, "Commentary on Romans"

(emphasis mine)