Kedoshim: Rashi’s Responsum: Rebuking Sinners
Rashi, in Responsum #40, deals with the Talmudic rule (Beitza 30a) that one should not rebuke sinners who offend unintentionally because it is better for them to remain ignorant that they are doing wrong than that they should be aware of it and continue to sin intentionally. In that case, what becomes of the Scriptural injunctions to rebuke sinners? Rashi replies that the Talmudic passage refers only to practices which the people have long held to be quite innocent. Even when they are told that these practices are wrong, they will continue in their ways out of habit. Here it is better to turn a blind eye. But where there is even a remote possibility that the sinners will acknowledge the error of their ways, it is a religious duty to rebuke them.