Just as, by definition, loshon hora is derogatory or harmful information which is true, so, too, is rechilus true information which can cause ill will. If the information is false, the transgression is even more severe. The Chofetz Chaim cites a series of verses (Mishlei 6:16-19) which state that a person who causes bad feelings between friends through rechilus is deemed a rasha (wicked person) and is despicable in the eyes of Hashem.
It is a serious mistake to think that speaking rechilus to someone who is already an enemy of the subject is not forbidden. It is. Though animosity was already present, it is forbidden to deliver a report which will deepen the rift.
The Chofetz Chaim warns us concerning another misconception, that it is not a sin to reveal information when pressured to do so. Consider this scenario: Your friend the contractor has just finished renovating a kitchen for your friend the homeowner. The homeowner was not completely satisfied with the job and he told this to some friends. Now you meet the contractor, and he says, “Someone happened to mention that you were present when Levi talked about the work I did at his house. What did he have to say?” If you hesitate before responding, he might say, “What’s the matter? Is he unhappy about something?”
At this point, you are in a difficult situation. If you say, “He’s not unhappy,” you’re implying that he isn’t particularly happy, either. If you refuse to discuss it, the implication is also negative. The best strategy, if you can anticipate this type of situation, is to prepare a quick, simple answer that will preempt further conversation about that topic. You should not relate what Levi actually said, despite the pressure to do so.
The Chofetz Chaim concludes that even if one’s father or rebbi (Torah teacher) asks him, “What did so-and-so say about me?” it is forbidden to say anything negative. Responding negatively to, “Did they like my shiur (Torah lecture)?” also falls under the category of rechilus. Here, too, one must delicately and respectfully avoid an accurate response.