I don't think this has anything to do with Brittain or geography but rather the language of the Angles, which is posited to form the primary substrate for modern English.

how are you defining “racist”?

Its odd that you immediately paint this as racist, when it is exactly what the "Académie Française" does and has done for centuries.

And, if you read into the site even a little they define Anglish inborn terms as those in use prior to 1066 after the Norman Conquest [1] of England.

This is an innocent conlang designed to highlight some interesting historical circumstances around a bloody and protracted conquest. That some people with Inborn Anglish ancestory have an interest in their own history is innocent and given current trends, perfectly reasonable.

I would suggest you examine you own biases before jumping to conlcusions, as I doubt you would make the same statements against any other culture seeking to document their history.

[1]: https://en.wikipedia.org/wiki/Norman_Conquest