Chofetz Chaim Daily 5 Av 8:3 Asur to say LH about a child if it will put him in a bad light or cause him damage. 8:4 Asur to say LH about an am haaretz. Saying LH on a scholar can often be in the category of mivazeh Talmid Chacham which is a terrible sin. Someone who’s a Rav and toils in Torah is considered a Talmid Chacham.
Chofetz Chaim Daily 6 Av 8:5 Mitzvah to say LH about a known apikores (one who denies anything of written or oral law) 8:6 If its a rumor, you can suspect and stay away, but do not believe it until you see it yourself or otherwise verify it. 8:7 Same laws apply for a rasha.
Chofetz Chaim Daily 7 Av 8:8 Some permit LH about baalei machlokes to cause those at fault to stop fighting, IF 1. you have good intentions & not hate 2. no other way to stop it 3. you’re certain this party is the guilty one. 8:9 There is a cherem against saying LH about dead people, especially Torah scholars & their teachings.