An attack upon an opponent in order to discredit their arguement or opinion.
The ad negrus fallacy exposes prejudice towards a set individual producing an argument, and its validity, based on skin tone or racial background.
Person A: It is crucial that we facilitate adequate means to prevent degradation that would jeopardize the project.
Person B: You're literally black, ebonically gatekept.
Person A: That's a fallacy ad negrus, me being black has nothing to do with the validity of my thoughts and opinions!