Perhaps the BBC is starting to get it.
How could it not? When people concentrate their energies on the things that make them different from each other - language, customs, religion, history - it can't help but drive wedges between them. A nation cannot survive if its people view the world in terms of us and them. People need to focus on the things that they share in common, the things that unite them and make them citizens, if they wish to maintain a viable society.
Theodore Roosevelt said over eighty years ago that, "The one absolutely certain way of bringing this nation to ruin, of preventing all possibility of its continuing to be a nation at all, would be to permit it to become a tangle of squabbling nationalities, an intricate knot of German-Americans, Irish-Americans, English-Americans, French-Americans, Scandinavian-Americans, or Italian-Americans, each preserving its separate nationality." Today we could add a couple more groups to Teddy's list, but it would only reinforce his point.
This is why multiculturalism is such a corrosive sociological phenomenon. Emphasizing differences by celebrating them is the surest way to erect barriers and to dissolve the bonds which glue a diverse people together as a nation. Indeed, that's perhaps the chief reason why the Left so enthusiastically pushes it.