Let's start with the simplest definition I could find, just to walk you through it.
> "(n) an authoritarian and nationalistic right-wing system of government and social organization."
Is this what DHH is advocating for? Absolutely. I'll skip past right wing because that part is obvious. Nationalistic in terms of "non-Londoners" being used interchangeably with immigrants, a person from Birmingham meets his "Native London" criteria, and using that criteria for social organization.
Pretty cut and dry for anyone using just the basic dictionary definition. Obviously, there's a version with more stipulations and exceptions you'd rather use but those can be safely filled under "overly esoteric".