The self-important slayers of ‘cultural appropriation’ have gone too far this time. Clearly they didn’t get a big-enough moral kick from chastising white people who do yoga (on the basis that yoga has ‘roots in Indian culture’), moaning about Beyonce donning a sari (‘how is this different from white folks wearing cornrows?’, the racial police demanded), and fuming about middle-class indie kids who wear Native American headdresses at music festivals (apparently this‘perpetuates damaging, archaic and racist stereotypes’).

So now they’re turning their fire on a black actress who, in their view, is not black enough to play Nina Simone. Yes, even black people can now be accused of being insufficiently black for certain cultural pursuits.

The actress in question is Zoe Saldana, a fine actress whose curious combination of vulnerability and steeliness has made her the darling of the modern Hollywood blockbuster. She’s one of the best things in the Star Trek reboot movies and she even managed to inject some humanity into James Cameron’s otherwise soulless, eco-miserabilist epic, Avatar. And next she will play Simone, in a big biopic, the trailer for which was released last week.

But the identity-politics mob isn’t happy. Why? Because Saldana is a light-skinned black person, a ‘half black’, as some have foully put it, and she used make-up to make herself as black as Simone.

The internet went into meltdown over this revelation. Saldana, who is Afro-Latino, was accused of 'blacking-up'. A writer for CNN said Saldana has resuscitated Hollywood’s ‘abhorrent history of blackface’. Simone’s own brother said Saldana’s turn as Nina is an ‘insult to our people’.

At the Telegraph, Emma Dabiri snootily decreed that Saldana is the ‘wrong black woman’ to play Simone. ‘With her long silky hair and brown tan skin, Zoe Saldana may well be black,' Dabiri generously conceded, but apparently she isn’t ‘black enough’. On Twitter, meanwhile, where reprimanding cultural appropriation has become a favoured and feverish pastime, Saldana is being mauled, slammed as no better than a ‘white actress wearing blackface’.

It’s so ugly. The intensity with which Saldana has been slated in the press and defamed on Twitter, having her skin colour and identity pored over and policed by racially correct identitarians, is a reminder of how vicious the politics of identity can be. People who pose as progressive, as enlightened and anti-racist, are ‘calling out’ a black woman over her skin colour, effectively branding her a modern-day minstrel, a ‘blackface’, a not-real black person pretending to be black. They can’t seem to see the twisted irony of claiming to be anti-racist while obsessing over a black woman’s skin and shaming her for having the wrong racial make-up. This isn’t anti-racism; it’s the very definition of racialism; it’s racial thinking, and racial shaming.

The Saldana shamers don’t seem to understand that acting is all about empathising with and entering into the spirit of someone who is not you. And actors frequently use make-up and prosthetics to become that other person. Whether it’s straight actors pretending to be gay, able-bodied actors pretending to disabled, or perfectly nice gentlemen hunching their backs and going psychopathic to play Richard III, acting is a pretence — and one usually driven by a decent, humanist, cultural urge to embody a character and allow people to understand him or her.

The logic of the fuss over Saldana is that, in the words of movie director Judd Apatow, ‘actors should only be allowed to play themselves’. It is now ‘offensive to pretend to be other people’, Apatow quipped.

The reason identitarians are so obsessed with acting — whether it’s Eddie Redmayne having the temerity to play a trans person or able-bodied actors playing disabled people — is because their obsessive judgement of everyone according to their biological, racial and gender identities has made them blind to the fact that human beings can empathise with and depict other people. In their mind, everyone should stay in their racial and gender boxes, and never write about, talk about, study or borrow from the cultures of people in other racial and gender boxes. Saldana should stick with her Afro-Latinos and not presume that she can understand the blacker experience. What a foul, divisive and fundamentally anti-humanist worldview.

The shaming of Saldana shows that identity politics has horrendously re-racialised public and cultural life. These so-called progressives have replaced the old politics of racism with a new politics of racial etiquette, where everyone’s speech is policed for unwitting ‘racial microaggressions’, our cultural pastimes are checked for any over-borrowing from ‘other cultures’, and we’re implored to be racially aware all the time. It’s a PC version of race-baiting, where every issue and every piece of culture is turned into a racial minefield.

Some of us don’t want to be racially aware. We don’t want to judge people according to their skin colour. And when Nina comes out, we will see, not a ‘half-black person’ mimicking a ‘real black person’, but a good actress doing her very best to capture the soul and life of another human being. That’s what humans do — we reach across made-up racial and cultural boundaries in an effort to understand and feel what other people feel.