Duty to defend

"Evil speaking . . . is a poison that extinguishes charity in both of the parties; so that a single calumny may prove mortal to an infinite numbers [sic] of souls, killing not only those who publish it, but all those besides by whom it is not repudiated."

"la médisance . . . est un poison qui éteint la charité en l’un et en l’autre.  De sorte qu’une seule calomnie peut être mortelle à une infinité d’âmes, puisqu’elle tue non seulement ceux qui la publient, mais encore tous ceux qui ne la rejettent pas."

     Blaise Pascal, Provincial letters no. 16, trans. M’Crie (GBWW, 1st edition (1952), vol. 33, p. 140).  Pascal attributes this to St. Bernard of Clairvaux (Sermons on the Canticles 24[.4] de vitio detractionis), but is only paraphrasing (Pléiade edition ed. Le Guern, p. 1266).  What St. Bernard actually says (SC 431, 245) is (as trans. Kilian Walsh, vol. 3 (Cistercian Fathers series 7), p. 45),

The venomous tongue strikes a blow at charity in the hearts of all within hearing, and if possible kills and quenches it utterly; worse still, even the absent are contaminated by the flying word that passes from those present to all within reach.  See how easily and in how short a time this swift-moving word can infect a great multitude of men with its sickly malice.

I have yet to read the whole.