People really like to misuse terms like fascism these days, huh…
How the hell is any of that facism
Racism could be a much better fit. The blog post in question: https://world.hey.com/dhh/as-i-remember-london-e7d38e64
The interpretation that raises some pretty interesting points about the inherent racism in the expressed worldview: https://jakelazaroff.com/words/dhh-is-way-worse-than-i-thoug...
There is, however, an interpretation that explains how this specific kind of racism can be seen as at least fascism-adjacent: https://davidcel.is/articles/rails-needs-new-governance
The question of whether he wants politics in the workplace is moot when he's making public blog posts like this. For the open-source community, the open Internet is the workplace. People aren't just going to pretend DHH didn't say what he said (in public, of his own free will, using his own megaphone) because he didn't post it to ruby-core@ml.ruby-lang.org.
I'm done letting these labels deter my rational thinking.
The racist part was him asserting he could walk down the streets of London and guess who was British. Given the disparity between his estimated number and the actual percentage of Brits by census (and the remarkable similarity to his number and the probable skin color of Brits by census), it is real hard to find the generosity to assume that he doesn't just mean "When did the Brits stop being white?" And that kind of thinking has nothing to do with immigration control and everything to do with believing that there's a right skin color to have.