Fair play to you for being open-minded and asking questions, as opposed to just shouting “woke”, which is how a lot of brain deads react when they see something they disagree with.
So the “British to be minority by 2066” is based on an old far-right conspiracy theory that black, Asian and mixed-race families are having kids at a quicker rate than all-white families, so that by 2066 the UK will be more than 50% non pure-bred pedigree white.
It’s a conspiracy theory, and very likely not accurate. But irrespective of that, the reason it’s racist is because it’s equating “pedigree white” as British and everyone else as not really British.
So someone who was born here, who’s parents were born here, but has brown skin, is not considered “British” by these people. To be truly “British” you have to come from an unbroken chain of whiteness tracing back to the Druids, according to these people.
If the plane had said “Britain to be majority non-white by 2066” it would have still be inflammatory and still had the same intention of stirring up fear and hatred, and inferring that non-white is somehowinferior to white.
By saying “Non-British” instead of “Non-white” it’s taking it a stage further by suggesting that non-whites are not British.
So kids could be born here, their parents born here, they could serve in the army and die for their country, but not be considered as “British” if their skin had any kind of pigment to it?
The intention of the message was to suggest that white is superior to non-white. You couldn’t really find a more racist message than that, mate.