Robert Leighton

The cure of an evil tongue must be done at the heart. The weights and wheels are there, and the clock strikes according to their motion. A guileful heart makes a guileful tongue and lips. It is the work-house where is the forge of deceits and slanders; and the tongue is only the outer shop where they are vended, and the door of it. Such ware as is made within, such, and no other, can come out.

Francis de Sales

While extremely sensitive as to the slightest approach to slander, you must also guard against an extreme into which some people fall who, in their desire to speak evil of no one, actually uphold and speak well of vice. If you have to do with one who is unquestionably a slanderer, do not excuse him by calling him frank and free-spoken; do not call one who is notoriously vain, liberal and elegant; do not call dangerous levities mere simplicity; do not screen disobedience under the name of zeal; or arrogance, of frankness; or evil intimacy, of friendship. No, my friends, we must never, in our wish to shun slander, foster or flatter vice in others: but we must call evil evil, and sin sin, and so doing we shall serve God’s glory.