Sefer Chofetz Chaim chapter 5 halacha 1

Today we started the fifth chapter of the laws of lashon hara which discusses speaking lashon hara about a person who transgressed a mitzvah between man and his fellow man. The Chofetz Chaim says that it is still forbidden to speak lashon hara about him even if it is completely true, certainly if there is some falsehood in the story. However this is so if there won’t be any harm to others, but if he becomes a possible threat then we’ll discuss in more detail in chapter 10 when and how it is permissible to speak out against this person. For now we are discussing circumstances where you witnessed a person not doing a favor for another, for example not lending a loan when requested, not giving tzedaka, acting with a grudge or revenge etc., where there is no threat of harm to anyone, in these circumstances you cannot tell anyone what you saw. Even if you see that this person never is nice, is apparently bad in nature and has a lack of fear in Hashem so does not care to fulfill these particular mitzvos, still in all the Chofetz Chaim concluded one cannot speak out against him though in other proactive cases where everyone knows   the transgression is wrong and still this person sins out of spite, it is permissible to speak lashon hara about this type of person since he takes himself out of the realm of “your nation” but in this case, either because you can only be excluded from “you nation” if you actively sin but in this case you are passive by not lending or giving tzedaka, or because we don’t really know what makes a person turn sour, mabe one time he leant money and wasn’t paid back so now he never leands money tough he is able to, this does not mean he is doing the right thing but you still cannot speak lashon hara about him. And if he did not do the favor to you then you will be committing at least two sins of bearing a grudge or even revenge along with speaking lashon hara by slandering him and spreading a bad name about him in public.