Kevin Deanna at Youth for Western Civilization has a post titled We're a Culture, Not a Costume Too |Selective outrage over Halloween costumes, about some "anti-racist" students at Ohio University who object to white people dressing up like them. For example, here's a poster featuring an Arab, who, living in America, dresses like Americans, (jeans, polo shirt)but objects to Americans dressing up like Arabs (bedsheet, headdress) on the traditional American festival of Halloween.
There also similar posters from people who don't want you to dress as campesinos, geishas, or in blackface.
They're serious about blackface. If you wear that at a fraternity party, the Administration will still be having fits by next year's Halloween, and in Canada, police have been called to investigate the reports that someone appeared in blackface at a costume party.
Multicultural types tend to refer to this kind of thing as a "blackface incident." So don't.