Daniel Defoe on migrant workers

Am reading A Journal of the Plague Year by Daniel Defoe, with a preface by Anthony Burgess. Burgess mentions Defoe's satire, the True-Born Englishman, written in 1703 and attacking xenophobia and intolerance of immigrants.

"These are heroes who despise the Dutch,
And rail at new-come foreigners so much!
Forgetting that themselves are all derived
From the most scoundrel race that ever lived!"

Three hundred years on and we still have xenophobia and intolerance of immigrants.
Later talk to a friend who says he often finds, when he gets home and takes off his coat, that he has been spat at . (He was brought up in the UK but his family originated elsewhere.) He generously says the people (who spat) just don't 'get' what he considers the essence of being British i.e. a core tolerance.

What is the essence of being British?