What is the proper use of insults?

I'm trying to understand the ethical use of insults and inflammatory language. How can I know when I ought to be offensive and when I ought to avoid it? There seems to be a tension within the Bible on this. For example, consider Jesus's words in Matt.5:22 > Whoever insults his brother will be liable to the council, and whoever says, 'you fool!' will be liable to the hell of fire. There are other passages which, in isolation, would seem to prohibit all use of insulting or offensive language: > In your hearts honor Christ the Lord as holy, always being prepared to make a defense to anyone who asks you for a reason for the hope that is in you; yet do it with gentleness and respect. (1 Peter 3:15) > Whoever belittles his neighbor lacks sense, > but a man of understanding remains silent. (Proverbs 11:12) > A soft answer turns away wrath, but a harsh word stirs up anger. (Proverbs 15:1) > Be angry and do not sin; do not let the sun go down on your anger... Let no corrupting talk come out of your mouths, but only such as is good for building up, as fits the occasion, that it may give grace to those who hear. (Galatians 4:26&29) > With [the tongue] we bless our Lord and Father, and with it we curse people who are made in the likeness of God. From the same mouth come blessing and cursing. My brothers, these things ought not to be so. (James 3:9-10) At the same time, we also read in the Bible many instances of Jesus and the apostles using insults: (From Jesus:) > You are of your father the devil, and your will is to do your father's desires. (John 8:25) > You Pharisees cleanse the outside of the cup and of the dish, but inside you are full of greed and wickedness. You fools! (Luke 11:39-40; in this whole paragraph Jesus is not very polite) > You brood of vipers! How can you speak good, when you are evil? (Matt.12:34) (From others:) > "You brood of vipers! Who warned you to flee from the wrath to come?" (Luke 3:7) > O foolish Galatians! Who has bewitched you? (Gal. 3:1) > I wish those who trouble you would emasculate themselves! (Gal.5:12) > I have written something to the church, but Diotrephes, who likes to put himself first, does not acknowledge our authority. (3 John 10) > These [false teachers] are hidden reefs at your love feasts, as they feast with you without fear, shepherds feeding themselves; waterless clouds, swept along by winds; fruitless trees in late autumn, twice dead, uprooted; wild waves of the sea, casting up the foam of their own shame; wandering stars, for whom the gloom of utter darkness has been reserved forever...These are grumblers, malcontents, following their own sinful desires; they are loud-mouthed boasters showing favoritism to gain advantage. (Jude 12-13,16) I could go on with many more examples but I think these suffice to prove the point that Jesus and the apostles *did* use insults and harsh words at times. I am wondering if anyone can point me to some good resources dealing with this tension. **Are there any works by respectable Christian authors dealing with the issue of the proper use of insults and/or offensive language?** I am coming from a Reformed perspective, but if anyone can recommend resources from other denominations as well, I would certainly take a look! To be clear about what I am asking, I'm not simply asking for a resolution of the apparent tension, but also for a practical set of principles to know when it is right to offend people. ---- Update: Since some have taken issue with my use of the word "insult", I ought to explain why I think it's the right word here. Jesus knowingly used language that was offensive to his listeners, and not just mildly so. If you want to call it a "rebuke" instead of an "insult" that's OK, but it doesn't change the underlying question I have, which is basically to what extent should I try to avoid offending people, and on the flipside, and when should I knowingly be impolite, as Jesus undeniably was on some occasions.