In 1960, American novelist Harper Lee wrote her masterpiece, To Kill a Mocking Bird.

It won the Pulitzer Prize, and was made into a film starring Gregory Peck. Among the central characters is Atticus Finch, a virtuous white lawyer, who defends Tom Robinson, a black man charged with rape.

The novelist wrote at a time when black masculinity was criminalised and innocent men were frequently lynched, framed and executed. Lee exposed the squalid, racist culture of her homeland and found hope in liberal values. Then she fell silent.

Decades passed. In the long-awaited sequel published this week, Go Set a Watchman, Finch has become a hard racist and segregationist.

African Americans greeted the new novel with relief.

A good friend, an academic in San Francisco, emailed: “Harper is finally telling the truth. Those guys like Finch, who pretended to be with us, were lying to themselves. They liked to be anti-racist heroes, but only when it suited them. Inside their liberal hearts and heads they are supremacists. My son married the daughter of a lawyer who loved Martin Luther King and all that. He refused to walk her down the aisle. So I did.”

He is a businessman, who wants to remain anonymous because he is worried about the consequences of speaking out.

A new American film, Dear White People, has just been released in the UK. Witty and caustic, it examines white privilege and black identity. It will pull audiences. We find strange comfort in tut-tutting about racism in America. It makes us feel morally superior.

No black Briton would dare to do something similar. It’s fine to make movies about long-ago slaves and the Raj. But to put stories of racially unjust Britain, here and now, on screen? Absolutely not. (Go on, prove me wrong.)

There is much national outrage when well-known people use words that are deemed offensive. But discrimination, prejudice, violence and common bigotry raise no concern these days. People of colour die in custody or during arrest; black graduates are kept out of jobs; apprenticeships are harder to get if you are not white; minorities are more likely to be stopped and searched and new migrants are seen as “cockroaches”.

The National Audit Office recently looked at the top civil service and found it to be almost wholly white and male. Researchers have found that ethnic-minority offenders are more likely than white offenders to be sent to prison and get long sentences. Black men and women cannot get into trendy clubs. Colour matters more than talent in almost every profession. Race-discrimination cases are much harder to pursue and most victims have given up trying.

Here she goes again, many readers will think, say, and tweet. Special pleading, guilt-tripping tolerant, white Brits. GET OVER IT. And anyway, the real bigots are black and Asian people, Muslims most of all – they who hate white folk, western culture, our freedoms. Terrorism is the real problem, they say. White working classes suffer more. Racism is so yesterday. Black is the new white.

I wish.

Frankie Boyle is rare among white men. He speaks up again and again against this perfidious, contemporary racism. And, many would say, crosses a line.

Raising this subject causes a bad smell, revulsion and odium. The messengers are denounced and cursed. Denial and complacency fight back.

The nation should be proud of how it has allowed talent to flower. Look at black actors Idris Elba and Chiwetel Ejifor, presenters Mishal Hussein and Reeta Chakrabarti, MPs Priti Patel, Sajid Javid, Sadiq Khan and David Lammy, novelists Kamla Shamsie and Andrea Levy, actors Mera Syal and Sanjeev Bhaskar – and so on, and on. Yes minorities can now reach for the skies, but most fall to earth, get hurt and lose hope.

Let me try and explain everyday, normative racism and how it works. Think about how people of colour are branded “controversial” when they are assertive; how white deaths matter more than brown or black deaths; how little black kids are called “ugly” in playgrounds, and trolls who attack us for our race and say we do not belong; the way we and our children are constantly asked where we come from; the way the media demonises dark-skinned people and how politicians describe us as trainee citizens on lifelong-learning programmes to become true Brits.

Men write in to tell me black and Asian women are hot and sexy: that is horribly racist, and also sexist. Those who ask me all the time why Muslims won’t integrate need to understand the bigotry inherent in that question. I am not responsible for those who live separate lives and choose to harm this nation and its people. The 7/7 bombers killed people of every nationality. I daily damn these ghetto mentalities.

This is not intended as a pessimistic dirge. Great Britain is a vibrant, cosmopolitan, modern nation, where love and friendships flourish between the races and ethnicities. But structural racism is back. The good news cannot offset the bad.

Writer and novelist Hanif Kureishi wrote recently on Enoch Powell’s abiding legacy: “Racism is the lowest form of snobbery. Its language mutates: not long ago, the word ‘immigrant’ became an insult, a stand in for ‘paki’ or ‘nigger’. ... people like Powell, men of ressentiment, with their omens and desires to humiliate, will return repeatedly to divide and create difference.”