I'm not very familiar with DHH, so he may have said and done some truly horrific things, but the author of this "viral blog post" lost me from the start:
I believe I read that article a while ago and wanted to read it again because I don't remember it calling for ethnic cleansing. After reading it very carefully looking for any direct or indirect calls for ethnic cleansing, I came up short. Never at any point in the article did DHH state that ethnic cleansing was a valid solution. As a matter of fact, he directly recognizes that it's not clear how they can undo the erosion of British culture in Britain:
I really feel for the Brits because it's not obvious how they get themselves out of this pickle.
The whole article seems to maintain the tone of a cautionary tale with the message "this is why you don't let erosion of your culture happen in the first place - because it's virtually impossible to recover".
Similarly, the author of the blog post claims:
In “Wolves, sheep, and gypsies,” he called for the ethnic cleansing of Romani people across Europe, comparing them to wolves.
However, after reading that article, he never called for any ethnic cleansing, especially not "across Europe", as he never mentioned any place in Europe outside of Denmark. As a matter of fact, his horrible solution to the problem was for the Romanis to make use of the shelters Denmark provides:
Copenhagen is the Danish capital. It's repeatedly been named the safest city in the world in recent years. Partly because it didn't tolerate vagrants and homeless people taking over public spaces (as has happened in so many American cities). Previously, police would tell someone they couldn't sleep or camp in the city, and they could go to one of the city-run shelters. But now that this is considered too cruel(?!), the native inhabitants of the city instead have to deal with literal shit on their way to the metro.
With all of that said, he may have stated or done some other things that are indefensible of which I'm currently not aware. But the way that "viral blog post" grossly mischaracterized the tone of the articles is emblematic of why people on the far-left are often seen almost as equally divorced from reality as people on the far-right.