No he should not! First of all, we must remember that Jesus taught that we are to treat others as we would want to be treated (Matt. 7:12). Even if we were in error none of us would want to be rebuked by being called “stupid” or an “idiot.” Second, a teacher or preacher of the gospel is called upon to “persuade men” (2 Cor. 5:10). Few people will be persuaded to leave error by insulting their intelligence or character. Even if someone is wrong in their practices or beliefs our efforts will prove counterproductive if we try to expose their falsehood by using this kind of language.
In addition to these practical concerns, Jesus makes it clear that Christians in general should not use this kind of language. Jesus taught all of His disciples, “You have heard that it was said to those of old, ‘You shall not murder, and whoever murders will be in danger of the judgment.’ But I say to you that whoever is angry with his brother without a cause shall be in danger of the judgment. And whoever says to his brother, ‘Raca!’ shall be in danger of the council. But whoever says, ‘You fool!’ shall be in danger of hell fire” (Matt. 5:21-22, NKJV). I used to think that this only meant that a Christian should avoid calling someone a “fool,” but a closer look at the text shows that there is more to it. The Jews seem to have imagined that the word raca (an Aramaic word of contempt) was an insult to be avoided, but thought little of using the Greek term mōros (translated “fool” in this verse). Our term “moron” is directly derived from this word. Jesus warns that using a word they considered acceptable could not only bring earthly punishment but eternal punishment.
Some, over the years have rationalized Jesus’ words to apply only to what the term “fool” infers about one to whom it is applied in Scripture. Robert Mounce, in his commentary on Matthew wrote, “The fool in Hebrew thought was not the intellectually incompetent but the person who was morally deficient. This kind of fool lived as if there were no God…” (45). Psalm 14:1 declared, “The fool has said in his heart, ‘There is no God.’” This has led some Christians to argue, “the point is what the term says about one’s relationship to God,” reasoning “I can call someone a fool (or an idiot), so long as I don’t mean it in that way.”
The problem with this reasoning is what we find in the rest of the New Testament record. After Jesus lays down the commands mentioned above, in apostolic example, while the term mōros may be applied to one’s estimation of himself (1 Cor. 3:18; 4:10) or to things that are “foolish” (1 Cor. 1:27; 2 Tim. 2:23; Titus 3:9), an apostle never calls someone a “fool (mōros).” We do see the milder term aphron meaning “without reason” or “unwise” (Eph. 5:17) directed by apostles to others (1 Cor. 15:36; 2 Cor. 11:16; 1 Pet. 2:15), but this word does not carry the sting or the judgment of a person’s worth that mōros does.
Is the term “fool (mōros)” any different in meaning from saying someone is an “idiot,” or saying he or she is “stupid”? No. While we might, as seen in the apostolic example mentioned above speak of a practice or belief as “unwise” (or perhaps even “foolish”) that is a different thing from saying the person is a fool, stupid, or an idiot. This is not the kind of language Christians should use, period!—especially if one is a preacher of the gospel.
For more on this subject read my article "Should Christians Call People Idiots?": http://www.olsenpark.com/Bulletins14/FS16.30.pdf or the sermon of the same title: http://www.olsenpark.com/Sermons14.2.html
Kyle Pope, January 2017