Briefly... libertarianismLibertarianism believes in The Invisible Hand of the market regulating the behaviour of everybody including consumers and companies and the small powerless governments it advocates. The reality is different. People are not naturally wise and rational consumers who vote with their wallets and consider each monetary investment. If people understand the concept of walled gardens and vendor lock in for instance, Apple and Microsoft would have not ever been able to lock people out of the stuff they themselves bought or prevented them from switching platforms at will. Smart consumers would just avoid them at all costs, even opting for inferior software. That is obviously not the case. I would like to expand on that problem some other time, but the fundamental error of libertarianism is based on its ignorance of human nature.
Communism and human natureCommunism suffers from exactly the same failure, but instead of The Invisible Hand of the market communism has the Invisible Force Of Community, a force that is equally lame and non-existent. The proof of this abounds. If you take a human being ask her if she would save 1 of her own children or 10 unknown children the answer is damn obvious. I bet you didn't even have to think of what she would decide. This natural tendency towards nepotism can be found everywhere in society from inheritances to the job for the nephew who is completely incompetent.
It has been studied extensively in primate models. Male chimps for instance spend most of their lives in the same troop. Females migrate into the group. The result is that male chimpanzees get along quite well, until you introduce another troop into their territory. There will be blood! Baboons on the other hand have males migrating from other troops and females remaining in a troop for life. Unlike chimps, they are real assholes to each other. No surprises there, this all seems obvious to most of us.
Not to communists. They believe we can modify human behaviour on a whim to make everyone care for everyone else. If they can't, then the whole system fails because families stick together and hoard resources, build alliances and give preferential treatment to friends and family. Not surprisingly if a stranger needs a lift to a neighbouring town I don't give a rat's ass, when it is my sibling I care. Friendship offers an even more complex challenge for a communist system.
Post-scarcitySome communists accept the human nature argument, or try to brush it off by announcing that someday scarcity will be a thing of the past. Unfortunately this ignores another tragedy of human nature: the Tragedy Of The Commons. When things are abundant we waste them. The other problem is that of want versus need. Want and need are basic economic principles and communism adequately addresses need, but leaves want out of the picture. If one person wants something in a communist society, it is not fair for that person to get it unless everyone can have that thing.
Behaviourism failedGive me a child and I'll shape him into anything. - B F Skinner
That was the brilliant psychologist B.F. Skinner who discovered that pigeons could become superstitious when they were fed randomly. Not so brilliantly, he thought that humans were kinda like pigeons. He thought that you can socialise a human being to behave in any way you wanted them to. Behaviourists were so dogmatic that they even refused to look at the brain and only focussed on behavioural stimuli and response. The whole concept was a drag on psychology for decades, and it seemed so nice that some people still cling to the idea. Communism relies on it. Everyone should be socialised to view everyone as a comrade with equal value, or else the whole idea is fucked.
Change in the human raceOne point that weakly reinforces behaviourism is that it is partially true. If there is a justice system there are less thefts than when there is not. Human behaviour can be changed to some degree, but it is much like a palm tree. We can bend it to the wind only to a certain degree before it uproots. We still have a long way to go to becoming a better species, but nowhere on that path can we be expected to ignore our families and pledge allegiance to some nationalistic god force.
So why the comparison with religion? Religion denies the sciences to fit its own world view. Project your image on the world and it will be so, or something like that. It is a direct contradiction of science because science tries to discover what nature is like, and how to best utilise it, not how it should be like to fit an agenda. That includes human nature. Communism stands opposed to the science that makes it an impossible idea, cementing itself into dogma, attached to an era in the 20th century where the idea of equality and modification of human nature seemed like lofty and realistic ideas.