There are two issues here. First, is it wrong to use “blackface” when the actress is black, or is it only offensive when a white person does it? The history of blackface is worth noting before that question gets answered. The theatrical makeup (which included burnt cork and greasepaint) was used by white performers during the 19th century in minstrel shows where white men donned black makeup with exaggerated features and acted out offensive stereotypes of black people, most notoriously “Jim Crow” and “Zip Coon”. By 1840, black performers were also engaging in the practice, which was later condemned by other black leaders, including abolitionist leader Frederick Douglas. When Vaudeville entered the scene in the 1880’s, black performers were only allowed on stage in “blackface,” and this is how many black performers got their start. The practice now considered racist, and rightfully so (just ask Harry Connick Jr.).
It goes without saying that this is a lazy casting choice. The filmmakers would have been far better off doing the leg-work required in finding an on-point unknown that is perfect for the part, or perhaps just cast the very talented Viola Davis. But since Zoe Saldana was chosen, let’s answer the question. While it might not be AS offensive for a black person to don blackface, it’s still offensive. It’s also a poor creative choice, because it’s extremely distracting. Zoe is talented enough to take us inside this role without looking exactly like Nina Simone. Furthermore, let this be a lesson to every actress who has relinquished their larger nose in favor of traditionally white standards of beauty. This is your face. And there is no need to remove its character. Sure I’m a biased person with a large schnoz, but I can play Streisand if they need me.