Racism exists, no-one can argue that it doesn't.
The letter responding to the Society of Authors was written following the Oprah interview in which news headlines were cynically manipulated to give the impression of widespread racism in the UK media.
One example was of a story slamming the girlfriend of a UKIP member who had said Meghan will 'taint' the royal family. The article was expressing outrage at her views and yet in Oprah the headline was obscured to make it seem as if the woman's bigotry was being quoted without comment.
There were further examples. Such was the outcry that members of the press requested a correction from Oprah's team but were ignored. Whipping up division does nothing to help the fight against racism, quite the opposite.
You mention the 'straight outta Compton' article which has already been debunked as the work of two LA journalists. And yet it keeps coming back, like the zombie article that it is.
Another episode that's usually relied upon is the Danny Baker tweet. If you're not aware of UK comedy culture the use of chimps dressed in human clothes is a frequent feature, we even had them advertising tea for years.
Danny Baker was a longstanding DJ at the BBC and there is no record of anyone thinking he is racist for all the years he worked there. You'd think someone would have noticed..?. I find it absurd to think he would choose that moment to reveal himself to be a closet racist knowing he would certainly lose his job and reputation.
Moreover, Danny was a well known contributor to a comedy forum where a famous figure was chosen every week to be imagined as dressed as a chimp and made fun of. The image of a baby chimp for royalty was a comment on the circus surrounding such events. Many of us can't bear the whole hoopla and find it ridiculous.
Again, Danny's tweet is a zombie tweet refusing to die and dragged out to 'prove' something even though it was online for all of 8 minutes before he realised that his intention had been misunderstood. It was rightly removed but he didn't deserve what followed.
https://medium.com/the-cult-of-stupid/in-defence-of-danny-baker-143a3bc339c0
I too can link to numerous articles describing a far more nuanced view of the UK. than you present here. The idea that we are somehow behind the US when it comes to recognising our colonial past is just nonsense. What do you think the Commonwealth is for? It is committed t the process of decolonialisation and a more equal world for all it's members. Charles is the Head of State in 14 countries out of the over 50 that are members. The RF are fully behind all countries moving to independence.
Looking back at the articles written in support of Markle, I wonder how many would change their minds now? Markle has weaponised race in a manner that is as cynical as it is self-serving. She didn't even know we have a Black History Month in the UK despite a college asking her to get involved. She wasn't interested, it didn't fit with her victimised persona. She had no interest in learning about the different communities in the UK. The royals had hoped she would be a positive role model especially in the Commonwealth but Markle didn't want to represent the UK, she only represented herself.
We can recognise the problem of racism but that doesn't make the accuser beyond reproach, as much as she would have liked to have been.
Racism, mental health, sexual aggression, these are the shibboleths that are used by bad actors like Markle to close down criticism and claim the higher moral ground.
I supported her at first and like many thought that. yes, it was a good expression of multiracial UK (a country by the way that has the highest number of mixed marriages of anywhere in Europe, she wasn't anything 'new') but when I saw how dishonest and lacking in integrity she was I changed my mind.
Right message, wrong messenger.