Chofetz Chaim Daily 14 Adar 4:7 One may publicly degrade the actions of someone who has no fear of G-d and clearly doesn’t regret his sins. He may be shamed until he mends bad ways. Do not judge him favorably. *According to contemporary Halachic authorities, even if the subject is a sinner, they will most likely be classified as a “Tinok Shenishba” e.g. someone who didn’t receive a proper Jewish education, or did, but has unfortunately had challenging life experiences, and we have to deal with him like with any other Jew. Therefore one may not defame them no matter what the circumstances. As with all Lashon HaRa questions, in case of doubt one should seek the advice of a Rav.
4:8 If one does not heed command of Beis Din (w/o valid excuse), publicly degrade him and record his actions in public records.
Chofetz Chaim Daily 15 Adar 4:9 If you see someone has bad middos, you may not badmouth him because he probably doesn’t realize the severity of his actions. Instead, influence him to change. 4:10 You may tell your children or students to stay away from a person with bad middos. However, you must explain why you are telling them.