The logic of this tweet seems to go along the lines of: "it's OK to have some non white people on
#NMUKITVGMB - in a tokenistic kind of way (because after all, it's not like they're essential of anything) - as a type of 'decoration' / evidence used to stave off criticism of being racist, but of course, because they're not fulfilling an essential role - the more of 'them' i.e.
#MetaphorVersusUsThem that you have the fewer 'legitimate' i.e. white people that you have to do the actual job". The 'give away' is the characterisation of a "British white person" i.e. a 'legitimate British person' (pointing to the idea that
#IdentityWhite is an essential attribute of Britishness). The tweet is an overt example of deep-seated
#OtheringDiscriminationRacism and strongly implies that the author feels under attack i.e.
#TheoryPoliticsOfFearAnxietyOfVictimisation as they struggle (resist) to engaged with contemporary society i.e. a
#TheoryPoliticsOfEternity if ever there was one.