I wonder if this outward display of corporate positive diversity is a manifestation of Sainsbury's becoming a part of Walmart...
My aunt has almost always shopped at Sainsbugs, and usually at the 'diverse' Crawley* store. She tends to wear a St Christopher necklace, nothing new or strange there, and never an issue when shopping. However a month or so ago, the (presumed to be Muslim, by way of her hijab) point blank refused to serve my aunt until she hid her necklace. Unusually for her, she didn't speak her mind, but stormed out of the shop in disgust. Personally I would have had the store manager out and possibly the police.
The sad reality is that anyone who doesn't 'bend the knee' is automatically deemed to be racist, and if you're white and 'bend the knee' you are deemed to have been racist by acknowledging your guilt... Why apologise if you have nothing to apologise for.
*Crawley, being a New Town has always been a pot of genuine diversity, and generally without significant cultural clashes... The shittier parts are generally poor/white, the posher parts generally white and well to do non whites, and the bulk of the town is pretty much a melting pot.