We do not know whether it is a foolish modern usage that tells us nothing about the tradition. [...] Unless and until we learn the origin of the writing in question we cannot evaluate it, and it does not inform our understanding of whether any blackface tradition is racist or not. (etc.)

We are not dealing with a tradition - rather we are dealing with a revival; a wholesale re-invention; a reactionary anachronism wholly at odds with the multi-racial complexities of English society as it exists today. It is, therefore, to the sensibilities of the contemporary enlightenment (so far as it exists in the folk world) that all such practices are ultimately answerable, and not to those of an imaginary past. Whatever the traditional / historical / folkloric / fakeloric origins of blacking up might be, there is only one possible reading of it now and to justify it otherwise is surely racist in itself.