View source for Scripture about "no personal attacks – attack nonsense"

Don’t accuse anyone’s motives because it is arrogant to pretend we can know them, according to 1 Corinthians 4:5 which says we can’t be sure of the motives of others until God reveals them on Judgment Day. 

Even Jesus, who had plenty of reason to personally attack Pharisees, patiently answered objections. 

The most righteous king of Israel, Josiah, died because he would not listen to the warning of a pagan foreign dictator, Pharaoh-Necho, a man normally not to be trusted, Isaiah 30:1-3, but through whom God had chosen, this time, to speak. 2 Chronicles 35:20-25. This is a sober warning to us not to paint anyone as not worth listening to. The most unreliable among us accidentally gets things right from time to time. And although we may be justified in limiting the time we commit to listening to people with a poor reliability track record, when we do listen we need to weigh their words on their merits, not on their source. Even God listens to us. Job 1 recounts how God even listens to Satan, and even accommodates Satan up to a limit. It is most arrogant of us to lift ourselves above God. 

And yet unlike God we are bound by time and must be stewards of it. Jesus said there is a point where we ought to give up reasoning with people: that point is when the person you are trying to reason with simply ignores you. This is the case when someone keeps talking to you but is “nonresponsive”: they ignore your evidence, talking as if it doesn’t exist; or they change the subject to avoid it. 

:Matthew 10:14 And whosoever shall not receive you, nor hear your words, when ye depart out of that house or city, shake off the dust of your feet. 

:Proverbs 26:4-5 say we should not answer a fool “according to his folly” lest we be like him, but we should answer a fool “according to his folly” so he will realize how foolish he is. Every translation on my computer turns this into that stark a contradiction. And yet we sense that the proper response to misinformation must indeed be a wise balance between opposite principles: if we respond, the danger is that we get mired down in nonsense. If we don’t respond, the danger is that nonsense goes unchallenged, and assumes it “won”. 
But the articulation in these verses of these opposite dangers is a clue to how to handle nonsense.

My translation, inspired by the following excerpts from Bible commentaries: “The way to respond to nonsense is not by jumping in the mud with it and just slinging negativity and nonsense all around at it. The time to respond to nonsense is when you can articulate a mirror to show nonsense what it looks like; for example by following the logical extensions of its claims to show they lead to conclusions the opposite of what it expects or wants.”

'''Adam Clarke''' (1760-1832) “The cause assigned for directing to answer, as plainly intimates that the sage should address himself to confute the fool upon his own false principles, by showing that they lead to conclusions very wide from, very opposite to, those impieties he would deduce from them. If any thing can allay the fool’s vanity, and prevent his being wise in his own conceit, it must be the dishonor of having his own principles turned against himself, and shown to be destructive of his own conclusions.” - Treatise on Grace. Preface.

'''John Gill''' (1690-1771): Answer not a fool according to his folly,.... Sometimes a fool, or wicked man, is not to be answered at all; as the ministers of Hezekiah answered not a word to Rabshakeh; nor Jeremiah the prophet to Hananiah; nor Christ to the Scribes and Pharisees; and when an answer is returned, it should not be in his foolish way and manner, rendering evil for evil, and railing for railing, in the same virulent, lying, calumniating, and reproachful language; 

'''Albert Barnes''' (1798-1870) Two sides of a truth. To “answer a fool according to his folly” is in Pro_26:4 to bandy words with him, to descend to his level of coarse anger and vile abuse; in Pro_26:5 it is to say the right word at the right time, to expose his unwisdom and untruth to others and to himself, not by a teaching beyond his reach, but by words that he is just able to apprehend. The apparent contradiction between the two verses led some of the rabbis to question the canonical authority of this book. The Pythagoreans had maxims expressing a truth in precepts seemingly contradictory.

'''Matthew Henry''' (1662-1714): Proverbs 26:4-5 See here the noble security of the scripture-style, which seems to contradict itself, but really does not. Wise men have need to be directed how to deal with fools; and they have never more need of wisdom than in dealing with such, to know when to keep silence and when to speak, for there may be a time for both. 1. In some cases a wise man will not set his wit to that of a fool so far as to ''answer him according to his folly'' “If he boast of himself, do not answer him by boasting of thyself. If he rail and talk passionately, do not thou rail and talk passionately too. If he tell one great lie, do not thou tell another to match it. If he calumniate thy friends, do not thou calumniate his. If he banter, do not answer him in his own language, ''lest thou be like him'', even thou, who knowest better things, who hast more sense, and hast been better taught.” 2. Yet, in other cases, a wise man will use his wisdom for the conviction of a fool, when, by taking notice of what he says, there may be hopes of doing good, or at least preventing further, mischief, either to himself or others. “If thou have reason to think that thy silence will be deemed an evidence of the weakness of thy cause, or of thy own weakness, in such a case ''answer him,'' and let it be an answer ad hominem - to the man, beat him at his own weapons, and that will be an answer ad rem - to the point, or as good as one. If he offer any thing that looks like an argument, an answer that, and suit thy answer to his case. If he think, because thou dost not answer him, that what he says is unanswerable, then give him an answer, lest he be wise in his own conceit and boast of a victory.” For (Luk_7:35) Wisdom's children must justify her.

'''Keil & Delitzsch Commentary on the Old Testament''' Johann (C.F.) Keil (1807-1888) & Franz Delitzsch (1813-1890) Proverbs 26:4 After, or according to his folly, is here equivalent to recognising the foolish supposition and the foolish object of his question, and thereupon considering it, as if, e.g., he asked why the ignorant man was happier than the man who had much knowledge, or how one may acquire the art of making gold; for “a fool can ask more than ten wise men can answer.” He who recognises such questions as justifiable, and thus sanctions them, places himself on an equality with the fool, and easily himself becomes one. The proverb that follows affirms apparently the direct contrary:

Don’t respect nonsense, but respect the person who spouts it. Jude said Michael the archangel would not even speak disrespectfully to Satan – so how arrogant of us, who are far less righteous than Michael, to speak disrespectfully to our neighbors, who are far less evil than Satan? (vs. 8-10)

Love doesn’t mean leaving another’s nonsense unchallenged. 

Jesus’ “Second Greatest Commandment” was “love thy neighbor as thyself”. Matthew 19:19. Jesus got it from Leviticus 19:18 “Thou shalt not avenge, nor bear any grudge against the children of thy people, but thou shalt love thy neighbour as thyself: I am the LORD.” The verse before gives an example of what it means to love your neighbor: Leviticus 19:17 “Thou shalt not hate thy brother in thine heart: thou shalt in any wise rebuke thy neighbour, and not suffer sin upon him.”