Answer not a fool according to his folly, lest thou also be like unto him.
It is wrong to debate with fools. They do not deserve knowledge or truth. Wisdom is too precious to waste on them. Wise men have better uses of their time. And arguing is a fleshly lust. For these reasons, it is a sin to debate with men who do not clearly display godly wisdom and righteousness. By doing so, you descend to their profane level.
You should say enough to shut their mouths, but anything more is folly and sin (Pr 26:5). They deserve no honor (Pr 26:1), and only a beating will truly help them (Pr 26:3). To keep them from thinking they are right, you may briefly refute their idiotic notions. Truth does not back down from any, but it has no obligation to waste its time on any, either!
Jesus plainly confirmed Solomon by teaching, “Give not that which is holy unto the dogs, neither cast ye your pearls before swine, lest they trample them under their feet, and turn again and rend you” (Matt 7:6). Jesus often rebuked the Pharisees, Sadducees, Herodians, lawyers, and scribes of His day, but He avoided any foolish wrangling with them.
If you debate truth with a fool, he will first despise your wise words and ridicule the precious things you tell him (Pr 23:9). You will degrade the truth by letting him mock and reproach it. He will then twist your words and use them against you, because his heart is corrupt with hate and violence (Is 29:20-21). Leave him alone, and let him rot!
Too harsh, you say? Jesus called them dogs and pigs – vile animals and perpetual examples of beastly cruelty and selfish greed, among other despicable traits. When told He had offended the Pharisees, He said to His apostles, “Every plant, which my heavenly Father hath not planted, shall be rooted up. Let them alone: they be blind leaders of the blind. And if the blind lead the blind, both shall fall into the ditch” (Matt 15:14).
How do you spot a fool? Easy. Listen to him talk (Pr 14:7), and measure his walk (Pr 20:11). A fool talks a lot, likes his own ideas, gets angry easily, always excuses his conduct, belittles others, prefers teaching over being taught, wants to debate most anything, resents authority, disdains convention, or talks profanely. A fool also does not live by the Bible and has no spiritual fruit, which is the true measure of wisdom.
Your flesh wants to get in the last word, or believes you can persuade him by reasoning, or thinks love will win the day, or sees no risk to your own soul (II Tim 2:24-26; I Cor 15:33). There is danger here, so Paul warned against the foolish questions or vain babblings of foolish men (I Tim 1:3-7; 4:7; 6:20; II Tim 2:14-16,23; Titus 1:14; 3:9).