Now, we're all politically literate folk here, I assume. I think we can say it's fairly understood that (1) The New Right are nutty fanatics (2) the New Right is often inspired by Ayn Rand (3) New Right philosophy, like Randian (sorry, Objectivist) philosophy is vicious, violent and at frequently at odds with reality.
This isn't the point of Monbiot's piece.
There are two rituals for professional, non-aligned left wingers to observe. First you must find something wrong with Marx/Marxism. Finding something wrong about Marx/Marxism is the first thing any leftie author wanting to peddle a theoretical innovation has to do: trees must die because Marx was wrong. Marx is inescapable. Attacking Marx in this way is a backhanded compliment.
The second ritual, less well observed, is Orwellian even-handedness. Rightists are team players, but there's a type of professional leftie who considers it the height of sophistication to attack their own side, which is all Orwell did, really.
This is the point of the article. The majority of people in the comment box (not the most representative sample of society, or even Grauniad readers, but hey) are talking about Marx, not Rand. Asked how Monbiot could compare one of the most erudite, educated and humane thinkers of the 19th century to a chicken headed fascist, he said:
I agree with you on Marx's erudition and insight, but to me the Manifesto contains in theoretical form many of the horrors later visited upon the people of the Soviet Union and some other communist nations. Dialectical materialism reduces humanity's complex social and political relations to a simple conflict between the “bourgeoisie” and the “proletariat”; ie the owners of property and the workers, by which Marx and Engels meant, basically, factory workers. Any class which didn't tick one of these boxes was either, like the peasants, shopkeepers, artisans and aristocrats, destined to “decay and finally disappear in the face of modern industry”, or, like the unemployed, was “social scum, that passively rotting mass thrown off by the lowest layers of old society”, with no legitimate existence in a post-revolutionary world. But the world didn't work like that, and the people who didn't fit had to be shoved under the wheel of history.
Anyone who has not read The Manifesto of the Communist Party may be impressed by this. The section Monbiot quotes from (and very approximately too) is the first section, Bourgeois and Proletarians: a basic history of capitalism, interwoven with simple prognostication about its future. The manifesto is very obviously not about post-revolutionary society. The grinding of certain classes under the wheel of history (Monbiot's phrase) is attributed, in the manifesto at least, to capitalism.
None of this is impressive, coming from a generally fine investigative journalist, but such is the nature, often, of ideological struggle.