What is Eum Qui Nocentem Infamat, Non Est Oequum Et Bonum Ob Eam Rem Condemnari; Delicta Enim Nocentium Nota Esse Oportet Et Expedit?

Legal Definition
It is not just and proper that he who speaks ill of a bad man should be condemned on that account; fur it is fitting and expedient that the crimes of bad men should be known. Dig. 47, 10, 17; 1 Bl. Comm. 125.
-- Black's Law Dictionary