Michael, good question- 
Here's an answer  by Dr. David J. Leonard on-line:"There is no acceptable reason to ever don Blackface. It’s not a joke, it ain’t funny, and it’s not some creative license that adds to the value of your artistic endeavors. Blackface has a long tradition that is part and parcel with white supremacy. It is part of a history of dehumanization, of denied citizenship, and efforts to rationalize, excuse, and justify state violence. From lynchings or mass incarceration, white supremacy has utilized dehumanization as part of its moral and legal justification for violence. Spare me your reference to “White Chicks,” the Chappelle Show. Stop with your references to satire. Spare me your dismissive arguments about intent and not being racially motivated. Blackface is part of the violent history of white supremacy. If you don’t know, now you know."

Michael, that's just one view, you can take it or leave it.  I do find truth in it but might question the "never."