To understand how to prevent negative speech let’s see how the Torah instructs us to judge other people. In our daily lives, we often make a character judgment even when we do not have all the information at hand… we naturally judge people in our minds, which eventually can lead us to talk about those people…. . Are they any guidelines as to how should we judge people?
The answer is: Yes. The Torah say that if somebody is a known Tzadik, an ‘exceptional’ person, a saint who 99% of what he does is good, when we don’t have the complete information, we must give him the benefit of the doubt and judge him favorably. From the other side, if somebody is a known evil person (rasha gamur) even if he seems to have a good intention, you should be suspicious of his ulterior motives. If the boss of the opposite gang smiles at you, run away as fast as you can!
But both cases are really extremes. Most people are neither saints nor killers… The question is: how to judge 99% those like us who do good things but also make mistakes…. The Torah says unequivocally: “betsedek tisphot amitekha” (vaikra 9, 15) “You should judge the average person as if he was a Tzadik” (the word betsedek is interpreted here as: “like the Tsadik”). In other words, always judge the average person giving him the benefit of the doubt.