A recent poll found that 84% of British BAME consider Britain to be somewhat or extremely racist. 64% have been racially abused to their face multiple times.
The problem is that many/most white Brits do not believe that racism is a serious problem. Sure it happens very occasionally, but it’s just the odd bad egg. They believe this because the powerful people they listen to in the media always tell them that Britain is a wonderful, tolerant country with no need of serious change in any regard whatsoever (least of all hereditary monarchy!). These people in the media view virtually every post 1930s development in Britain as something negative. They liked the 1920s/1930s - or at least believe they would have done.
Of course, they are always reasonably wealthy in this fantasy imagination role play, not one of those who dies in their forties from preventable illness, probably related to slaving away for the aristocracy.
Anyway, so many/most white Brits do not believe that racism is a serious problem. So any time racism is in the news, the default starting position of about half the country is to downplay, or to put it down as exaggeration or as cultural misunderstanding or that the situation is politically motivated etc etc.
They mostly like the thought of living in a tolerant, multicultural(ish) country as it feels good and they get to experience some of the benefits. But they don’t like hearing anything negative from those minorities which calls into question their rosy view of things.