I once discussed how careful we must be with our words when mentioning the care we must take in discussing biblical characters or personalities. Yet there is even more cause to be careful with our words, phrasing and manner of speaking (and by this I do not mean speaking ill of others or taking care regarding lashon hara, but even one's conversation with a friend!), as explained by R' Hirsch below.
God has made sensitive man's soul, capable of being pained by every harsh touch, and yet He created this tender, sensitive instrument so that it may be the holder of the most sacred blessings of the human being, of honour and serenity, respect and love, of every enjoyment that life can provide, of every worth-while feeling of happiness, and of every emotion which links man to life and to his fellow-men. As long as it exists clear and serene within the human being, so long will he remain happy, however hard he may be hit by external events. But once it is wounded and saddened, and its peace disturbed, then the human being becomes sick and withers like a crushed flower. You should hold sacred man's inner sanctuary, consider it as God-given soil in which to plant your most beautiful blessings, wisdom and solace, love and kindness. And for this purpose you were given that most noble gift- the word.
But if you turn into a sharp and lethal weapon this word which is destined to bring life and blessings; if you seek pleasure in mocking the inexperienced and less intelligent, in deceiving and embarrassing him instead of teaching and correcting him; if you ridicule the unfortunate whose troubled mind is longing for comfort from your lips, and overwhelm him with useless reproaches; if you put your brother to shame in front of others even for the purpose of correcting him; if you degrade your brother's personality by calling him bad names; if with icy scorn and fiery disdain in your barbed words you shoot sharp arrows into your brother's heart and rejoice in his discomfiture- oh then, do not dare to look up to heaven! God sees your brother's heart convulsed by the daggers of your words, frozen under your icy scorn, humiliated under your ridicule. With Him the rejected soul will find refuge, to His Throne tears always find the door open. And you? The Almighty is just!
Youth and maiden of Israel! You to whom God's gift is still pure, whose hearts have not hardened, watch your word, keep it pure and devout, so that no heart may bleed, wounded by your word. Again, above all, watch it in your dealings with the unfortunate, the poor, dependants, servants; for doubly do they feel the slightest suggestion of scorn, indeed, their tender heart often feels a sting where you would not suspect one. And above all the female heart! Remember the teachings of our wise men who list as prohibited according to the prohibition of ona'ah (vexation): teasing, deceiving, embarrassing, needling, ridiculing; mocking, jesting with, and calling names, and then add: graver even than injury by action is vexation by words. The former only affects property, the latter the human being as a whole; the former can be repaired, the latter cannot; the tears of the offended find easy access to the Throne of the Almighty: fear Him, for His eye sees (Ch. M. 228).
Elsewhere it is said: He who puts his neighbor to shame in public is like a murderer; do you not see his blood flow? Three sinners descend into the Gehinnom and do not rise again: he who commits adultery, he who puts his neighbour to shame in public; and he who calls his neighbour names. Though all the gates of Heaven may be closed to prayer, no gate is ever closed to the tear of an injured heart.
~Horeb: A Philosophy of Jewish Laws and Observances, III Mishpatim Chapter 51, "Restriction, Oppression and Vexation", pages 257-258 by Rabbi Samson Raphael Hirsch