I understood the "extremist violent rhetoric" to refer specifically to accelerationists (in the states, we have the Boogaloo boys, but there are others), whose explicit goal is to accelerate the (from their perspective) inevitible collapse of the current order, to replace it with their own order. Often times, but not always, this is married to a both a doomsday-prepper I-can-go-it-alone mentality, as well as a libertarian theory of government.
Because unlike other kinds of extremist, violent, revolutionary political movements, those from the accelerationist + prepper mindset are explicitly opposed to modern life. Think Ted Kaczynski (that is, the Unabomber).
Not all violent extremists are focused on tearing down the modern technological order. ISIS, for instance, is only interested in the end of modern morality, but (evidently, based on their PR/recruiting arm) have no special qualms with modern media technology, industrialization, etc. The Red Army Faction was only opposed to the modern (at the time) government of Germany and a poorly defined concept of capitalism. But there is a specific kind of violent extremist who thinks that computers and mass production and factory farming are the problem. And I understood the GP to be referring to them.
