The author seems, to a large extent, to be talking about science fiction writers. Science fiction was great in the fifties, but it’s come to be dominated by a coterie of Leftist political activists.
And, for that matter, so has every other genre.
The new issue is the deliberate banning of science fiction authors from conventions like Jon del Arroz, John Ringo, etc. Where liberals threaten violence if the person shows up so the convention bans them, or in two of the cases in the blog and Kevin Sorbo at another event, “We say you’re emotionally dangerous as a conservative, you’re banned”.