Today is the 12th of Tamuz, 5770
'Giving the benefit of the doubt' (betsedek tishpot amitekha) is the best way to avoid Lashon haRa (negative speech) and all the things that cause it.
I'm coming out from the market with many shopping bags in both hands. I don't have a car. Suddenly, when I'm about to cross the street to take the bus my next door neighbor (who knows I don't own a car!) passes by and to my huge disappointment he does not stop to offer me a ride… My first 'impulse' is to think "What a bad guy!". That thought might trigger feelings of hatred (one Torah prohibition), seeking revenge (another Torah prohibition) and eventually making some negative comments about his terrible behavior to my friends and family! (third Torah prohibition).
The Mitzvah of giving the benefit of the doubt consists on stopping 'negative' thoughts before they become hatred, revenge and Lashon haRa.
When I see that my neighbor does not stop, I have to force myself to have second thoughts, this time advocating for him. Why didn't he stop? May be he didn't see me. Or maybe he wasn't going home, but somewhere else. To the doctor or to pick up his son and his schoolmates from school…
Giving the benefit of the doubt aborts the whole negative emotional process: hatred/revenge/Lashon haRa before it is born.