I'm going to ask you if you genuinely think that many of the POC posters here have not spoken about racism in the UK in context of these threads when many posters, again on this very thread, actively deny that there is racism here especially because of who says it.
I haven't read every thread, or every post on every thread I have dipped into. The back and forth of personal insults and accusations and counter-accusations...who's got time for that? As far as I'm aware, only a small handful of posters have denied that Meghan Markle has been on the receiving end of racist media coverage, and there were corrected and/or deleted promptly. It's provable fact that she has.
I see a fair amount of posts which are undeniably dogwhistle posts. They're called out, each time, and thank you to those who do so. I also see A LOT of posters deny that their negative opinions of Meghan Markle are race-based. I believe them because I agree with them. It's possible to have negative opinions of Meghan Markle which aren't based on race. I have negative opinions of my own (non-white) mother which aren't race-based! It takes time to sift through them and see each one for what it is.
I bet, like me, you rolled your eyes well into the back of your head when Harry came out with his "I've been made aware of my unconscious bias" rubbish. Did you, like me, feel he's about 400 years behind your community in this realization, that you have no time to waste waiting for him to catch up? That he's so far behind he won't ever catch up enough to even be able to insult your intelligence? When some posters insist on imputing racist undertones to negative commentary it feels exactly the same. Don't insult my intelligence. You may think you're convincing lurkers, or speaking up for POC. Perhaps you are. But not always. People who actually do have that racist undertone (or worse), you're pushing deeper into their belief system. That's polarisation, which is singularly dangerous. And people who fundamentally agree with you but just don't know: you're losing them by trying to tell them what they think. It's one thing to say "when you say x, this is what a POC hears", and another thing to say "you are racist because what you said actually means this other thing".
I don't mean this as a personal attack on you, and you're not singularly responsible for every anti-racist post on this board!! And, it cuts both ways, of course it does. Just, the discussion isn't advanced by a jackhammer approach to calling out everything that might possible be interpretable a particular way. Sometimes it is, sometimes it isn't. Like in real life.