If you are a professional actor performing a role and you need to alter the color of your skin as part of that role, you can do it. Robert Downey Jr. and Roger Sterling spring to mind. Dave Chappelle and Eddie Murphy have done it (though going from black to white isn’t even the same thing as going from white to dark).
If you are anybody else, you can’t. You can’t do it for Halloween; you can’t do it “ironically.” You just can’t wear blackface. If you do, you are a racist. Wearing blackface in public for fun is dispositive on the issue of your racism. And it’s dispositive on the issue of your own intelligence and creativity: if you can’t pull off the costume without darkening your skin, you’ve probably missed the point of your costume. It’s not like I’d need to wear whiteface to go as [trying to think of the whitest white person] Boss Hogg.
These are simple rules that have been with us for years, but people still keep screwing up. And when they do, it touches off a “conversation” about race — as if we need to talk about why some racist people wore blackface and thought it was okay.
Why did these law students dress up in blackface to go on a pub crawl? Because they’re racist, the end….