So here is my two cents, as an anarchocaptialist.
This article should probably be re-titled as "the Social Democratic Case against Anarchocommunism" because that is consistent with the messaging and content, and it would then be technically true (the best kind of true). However, anarchocommunism is not the only flavour of anarchism, and as such, to only discuss anarchism in terms that the communists use is illogical (composition fallacy) and a massive oversimplification of the term "anarchy".
Voluntaryists such as myself are in favour of a entirely decentralised society, one where as few as possible points of centralisation exist. We also know the value of capitalism & voluntary hierarchies as a solution to societal issues, and recognise the failures placed at capitalism's feet are largely due to government policies creating unintended market consequences.
I note that @ekklesiagora mentioned:
"Decentralized can be just as fascist as centralization. Centralization can lead to more libertarian outcomes. I mean, the centralized policing in Norway is more libertarian than the decentralized anarchic policing of South Africa."
My rebuttal to this is simple: How can a state police service (South Africa) be an example of decentralisation? What is being describe is a less free state being compared with a marginally more free state, but it is not an anarchistic policing solution, and especially not a voluntaryist one. At best this is a strawman argument, unless some evidence is provided demonstrating how South African security & justice markets are not under state control.
As for William Morris, let me use your own words against you:
"William Morris, as a democratic socialist, argued that socialism will bring about social equality and eliminate class structures, so that hierarchies and the domination of man over man will be eliminated."
And he was WRONG. Socialism did not bring social equality, did not eliminate class structures and hierarchies, and has not removed the ability to have power over others when & where it has been tried. In fact, it is logically incapable of doing so, because it requires the collective to be more important than the individuals with it, and it requires collectives are given the means of having agency (the state). The same is true for communism at its core.
Groups naturally do not have agency, because there is no single mind governing the group. Only individuals have agency, and because of this the concept of socialism, indeed any form of collectivism, is inherently flawed from a logical perspective.
I have no problem people voluntarily working together, and expending their collective effort for a common goal, or voluntarily agreeing to live as part of a democracy. Those concepts are not unique to democracy or socialism, however, and in some cases within those systems of organisation, the "voluntary" bit is optional. From experience, it is rarely taken into consideration.
Voluntary actions are inherent in capitalism, however, and capitalism has never required a state in order to work.
As for Popper, though I admire his philosophy regarding science and the scientific method, he for some reason fails to apply the same reasoning here. His arguments on exploitation ignored Hume's guillotine. A government is and will always be unable to optimally regulate markets of any kind, because it cannot know all of the inherent needs and wants of the market and all the consumers within it. Its attempts at doing so inherently are examples of the administrator's fallacy, just as the concept of democracy itself is a glorified bandwagon fallacy through and through.
First, I'll start by saying that I define anarchism as “libertarian socialism.” That is, classical anarchism. Anarchy means “no rulers,” and anarchists have traditionally taken that to mean no kings, no bosses, no landlords, etc. The kind of rulers that arise from capitalistic property are still rulers. Communist anarchism proposed communal ownership with democratic management. (Cf. Kropotkin, Malatesta, Bookchin) Mutualism and collectivism had a more nuanced approach, still with some sort of public ownership and democracy. (Cf. Proudhon, Bakunin) Then there was individualist anarchism, which wished to abolish allodial and fee-simple property, as we have under capitalism, and replace it with usufructuary private property and totally free markets. (Cf. Benjamin Tucker, Thomas Hodgskin, Lysander Spooner) In all cases, anarchists criticized rulers across the board. They disliked political rulers (kings/politicians), disliked official rulers (cops/theocratic priests), disliked economic rulers (bosses/landlords). “Anarcho-capitalism” is a departure from classical anarchism. While it has anarchistic tendencies and influence, it is not entirely anarchist. I don't call an “anarcho-capitalist” an anarchist for the same reason that I don't call a kid throwing a brick an anarchist. Anarcho-capitalism says that it is okay for people to be ruled over by bosses, because they have voluntarily entered into that arrangement. They say it's okay for a landlord to make rules for his tenants, since the property they live on is his. Thus, anarcho-capitalists consider any sort of rulership deriving from legitimately acquired property as being justified. Regardless of whether or not it is true that property can justify rulership, it is the case that anarcho-capitalists support some types of rulers that classical anarchists rejected, so anarcho-capitalism is a departure from the anarchist position.
Furthermore, when I was an anarchist, I identified with the classical anarchist tradition, being influenced mostly by Proudhon, Bookchin, and Benjamin Tucker. I advocated a free market with either usufructuary or Georgist private property within a system of democratic confederalism. Plus, anarcho-capitalism didn't exist when Morris and Shaw wrote these critiques of anarchism. So, it made sense to exclude "anarcho-capitalism" from the discussion.
You said: ”How can a state police service (South Africa) be an example of decentralisation?”
I was actually referring to the decentralized and competitive private security forces in South Africa, which operate much like the system that anarcho-capitalists advocate. Check out Law and Disorder in Jahannesburg. Btw, there actually are some aspects of Rothbardian security theory that I agree with, which I have written about here.
You said: “And he was WRONG. Socialism did not bring social equality, did not eliminate class structures and hierarchies, and has not removed the ability to have power over others when & where it has been tried.”
Actually, democratic socialism in Norway, Sweden, Denmark, Iceland, Finland, has done exactly that. And these places only ever went partially socialist, not fully socialist. Where “socialism” has not worked is in places like Russia, where socialism was NEVER tried. Lenin, following Marxist analysis, thought that socialism could only come about with the full development of capitalism; cut-throat competition would lead to monopolies, which would then naturally be taken over by municipalities like natural monopolies such as water and electric companies were. Since Russia had a pre-industrial agrarian society, rather than a competitive market, when the Bolsjeviks took power, Lenin believed that “State Capitalism” (Lenin’s own term, btw) would have to be employed rather than Socialism. Instead of worker-owned cooperatives, Lenin opted for government-owned industry—State Capitalism, not Socialism. He thought that eventually the State would “wither away” and socialism would naturally emerge. Either way, I am more of an advocate of distributism rather than socialism, so it’s a moot point.
Also, you mentioned “communism” as requiring a State. Actually, that's completely untrue. Communism is defined as a stateless and classless society. Such things do exist, but usually only in small tribal “primitive” communities. There's a great deal of sociological and anthropological literature on the topic. (Cf. David Graeber’s works on anarchy in Madagascar and James Scott's The Art of Not Being Governed) Also, the communist idea of “from each according to ability, to each according to need” is the bedrock of our society, what governs our relationships with families and friends. You don't tally up points when your kids get food from the pantry. This is what David Graeber refers to as the "communism of everyday life"; sociologists and anthropologists have been talking about this for a couple hundred years now.
You said: “capitalism has never required a state in order to work.”
Actually, the opposite is the case. All real stateless societies have been based on primitive communism or gift economies. Capitalism has only ever emerged where States have come into being. One government invaded another, looted, and took all the gold; they then minted the gold into coin, gave it to the soldiers as payment, then required the subjects, conquered people in general, to pay taxes in this government-issued coin. The necessity of acquiring the coin in order to pay taxes created a general demand for it, bringing markets into being. Barter, contrary to classical economics’ claim, never arose anywhere until after monetary systems had existed and collapsed. There is a great deal of archaeological and anthropological literature and research to back this up. (Cf. David Graeber, Debt: The First 5,000 Years)
You said: “A government is and will always be unable to optimally regulate markets of any kind, because it cannot know all of the inherent needs and wants of the market and all the consumers within it.”
I am familiar with the arguments against central planning. I actually agree with them, as does Karl Popper. That’s why both myself and Popper advocate markers for the distribution of goods rather than central planning. You should check out my post Markets Are Not Perfect, where I look at a few instances of market failure and how government intervention can rectify the problem. And, for the record, I am both pro-market and against central planning.
You should check out Markets Not Capitalism (book) for a look at a more classical market anarchist perspective, one that isn't exactly anti-Rothbardian btw. Also, maybe check out Benjamin Tucker's Individual Liberty, a classical market anarchist work. Tucker and Spooner heavily influenced Rothbard.