Based on his own blog post (https://web.archive.org/web/20250925050154/https://world.hey...) I would argue he does come off as racist.

There are a lot of non-white british people (just like there are non-white americans), and he basically ignores that entire population. He assumes that you are only british if you are white and that london is worse now because there are less whites there. That has nothing to do with meritocracy, and arguable little to do with cultural non-fit.

There's a lot more to unpack in that article aside from just that, but that is the most blatantly obvious one.. And for what it's worth, I don't disagree with DHH on mass immigration. But he seems to have a lot more severe beliefs than just "mass immigration is bad".