They're not though generally... there were a handful of openly racist tweets on Twitter posted directly to the tl which got attention, I saw 4 that were screenshotted and widely criticised - one "comedian", one (alleged) Estate Agent (or, he claims, a 3rd party using his account - of course, he would say that) and 2 apparent Somali guys LARPing as England fans.
Then there were the mostly foreign accounts, quite likely bots, spamming monkey emojis in replies on Instagram etc..
Contrast that with the general condemnation en masse of those few tweets vs 2/4 of the prominent ones being clearly faked and over 70% of the dubious replies Foreign trolls.
It's been amplified by the media because racism is a big topic at the moment, in reality, the UK is probably one of the least racist societies on the planet... even when comparing to European countries with far more right-wing politicians/political parties getting wider support and far-right football supporter groups and forget about Africa, Asia, South America, that's a whole other level.