Chofetz Chaim Daily 13 Av 9:5 Mitzvah to restrain even your young children from LH so they’ll get into the habit. 9:6 Asur to repeat private matters heard from a friend.
Chofetz Chaim Daily 14 Av 10:1 Mutar to spread the injustice that ploni caused your friend IF it will help to right a wrong, or defame wrongdoers. 10:2 However you must fulfill 7 conditions: 1. absolutely factual 2. certain who the real villain is 3. rebuke perpetrator first 4. must not inflate crime 5. L’toeles & no personal benefit 6. first try other non LH solution 7. outcome must not be worse than Beis Din would mete out.