Were you to apply the directions given for judging immorality to fatal error touching our Lord's person, you would have a very insufficient measure of discipline. False doctrine does not touch the natural conscience as gross conduct does. Nay, you may too often find a believer drawn away by his affections to make excuses for those who are fundamentally heterodox. All sorts of difficulties fill the mind where the eye is not really single. Many might thus be involved who did not themselves hold the false doctrine. If I accept the principle of dealing with none but him who brings not the doctrine of Christ, it will not do; for there may be others entangled by it. What is any individual, what is the church even, in comparison with the Saviour, the Son of the Father? Accordingly, the rule laid down by the Spirit for vindicating Christ's person from blasphemous assailants or their partisans, is infinitely more stringent than when it is a question of moral corruption, be it ever so bad.
Lectures on the Gospel of Matthew, page 324.