There are times when sharing negative information about others is allowed. As we discussed yesterday, even if one knows that someone transgresses a certain prohibition, there are some mitzvos that people are simply unaware of. To publicly denounce them for violating such commandments would be forbidden.
This would seem to indicate that if it is a mitzvah that everyone is aware of then it would be permitted. Not so fast, says the Chafeitz Chaim. We all slip up and people make mistakes. It is possible, he argues, that the person who did whatever it is we witnessed them do has changed their ways. To publicize what they have done would not only serve no purpose but be wrong. (We are not discussing a situation where a person is a potential threat to others. There are other considerations to take into account for such scenarios.)
A good example of this is something that made headlines in Jewish publications recently. A certain Jewish publication published findings of their own private investigation – they discovered that a certain prominent scholar in Judaic studies used a pseudonym to post comments on-line and in journals to defend and praise his own works. This was obviously unethical behavior and totally inappropriate for a scholar of any kind, most definitely of Jewish studies. However, this scholar had ceased using this pseudonym a while back. He clearly had felt, whether it was from remorse or fear of being caught, that it was not a good idea. For the newspaper to publish such information is a clear violation of the lashon hara discussed above.