From: Rabbi Moshe Sofer
To: Rabbi Hersh
The Chasam Sofer rejects the interpretation that lashes for calling someone 'mamzer' are based on the father's sin, ruling instead that the lashes relate to the defamation of the person himself as one destined to violate the mamzer prohibition. In a practical case where Rabbi Itzik called Rabbi Moshe 'mamzer ben mamzer,' he rules leniently due to provocation, instructing Beis Din to offset the relative fault of both parties and follow local enactments rather than strict Talmudic law.
Source: Shu"t Chasam Sofer CM §181