> Any sane implementation of anarchocapitalism provides a legal mechanism for forcing violent dude to not kill other people.

And that mechanism does not rely on political authority (it's not "legal" in the sense to which you refer, sanctioned by a political authority holding body). This is the critical point that you keep on utterly missing or mistaking for some semantic point that is not important so I'm going to try and be really specific about why this is important and why it doesn't fit into the example you've constructed.

Let's lay out the scenario you used in the current system and go through where political authority comes into play;

Guy wants to kill people for fun.

Everyone tells the guy it's not allowed.

The guy tries to do it anyway.

Because it is against the law, which is a set of rules defined by a singular monolithic body imbued with political authority, agents of that body step in to either stop the event from taking place or clean up afterwards in accordance with the law defined by that singular monolithic body. Self interest, non aggression and natural law don't come into it at all, it's simply an execution of "the rule of law".

And what is the rule of law? Whatever the holders of political authority say it is, your consent is irrelevant, your opinion is irrelevant. You have a duty to obey the holders of political authority because that is the entire point of the idea, they have absolute power over you and you are supposed to behave in accordance with the rules that they write because they hold political authority. Force is only being used in accordance with the rules of political authority in this scenario.

There have been instances in history where political systems didn't even consider it murder to kill specific classes of people for fun, the interests of the potential victim were never the point in a political system, it's always just been about the maintenance and expansion of political authority. Police can be corrupt and incompetent, the military can be decrepit and outmoded, none of that matters. All that matters is the head of the body politic gave orders and they are being obeyed.

As opposed to;

Guy wants to kill people for fun.

Nobody tells him "it's not allowed" in the sense that is discussed above. People would point out it would be extremely bad for his health to try, potentially, but the justification for this is not political authority or the rule of law, it is because the people he wants to kill for fun don't want to be killed. That is irrelevant in the case of political authority as opposed to the most important thing in this instance.

A competitive market arises for security providers that offer security to potential victims of aforementioned crazy psychopath. These providers have no special legal privileges and are not imbued with any specific powers that anyone is supposed to respect and nobody owes them a duty of anything. If they want to accrue and keep customers they must offer good service. If they are not competitive with other providers in the same sector they will cease to exist.

Their motivation is entirely focused on protecting the interests of their subscribers, maintaining and propagating their political power never comes into it, there are no elections to buy, no politicians to swear fealty to, just the single very simple equation; are they competing well in the market. Nobody can exploit their position of political authority which would allow them to evade actual accountability for their performance, they cannot levy a tax to pay for their incompetence despite abysmal performance, they have no special powers or privileges and any other agency may arrive at any other time in order to outcompete them if they see an opening in the market to be exploited.

This is what I mean by constantly restating the fact that it's not a political system or ideology. There is no political authority employed by any of the participants within the system, and thus it is not vulnerable to any of the myriad failings which plague all political systems. This is not sleight of hand or defining away the problem, it is a very critically important point.

> Democratically selected reforms to specific problems with solutions selected on the basis of scientific discussion of the evidence.

This seems like a contradiction in terms, democracy and scientific evidence have nothing to do with each other. So which is actually important? If it's scientific evidence you have yourself a dictatorship, if it's democracy you have mob rule.

> Even if the idea is good, claiming that you know things will work out because you "thought through the common objections" is nothing more than conjecture and blind faith

I don't know things will work out, I think the extensive discussion of the edge cases is pretty good, and certainly enough that it should at least be tried (which is already a near certainty with all the various seasteads and ZEDE's that are in setup mode around the world anyway). I do know that political authority is proving an achilles heel in all systems of social organisation around the world, but that is not a claim that something else is a silver bullet to fix that problem, just that the problem exists and appears to be intractable with the current paradigm of political authority holding bodies.

> There is no way to know how a society will behave, and the central implicit assumption tying everything together is almost always "everyone is like me and wants to live in a world I would like living in".

No, that's a large part of the reason for discarding the concept of political authority. Nobody should have the right to a special position that gives them the ability to define how everyone else must live their lives and how the world must be organised.

> People behave sub-optimally and violate game theoretic axioms of every variety.

And when they do, and there is no political body to back them up, at least it will be they who suffer the consequences and are outcompeted in the market, thus fixing the problem they represent rather than instituting ever increasing burdens on the sectors of society that do not similarly fail. When a state behaves sub optimally and violates game theoretic axioms, it just forcibly extorts the price of its malfeasance from its captive subjects by virtue of its position of political authority.

> Believing this is why revolutionaries have a nasty tendency of chopping off the heads of lots of people they should essentially agree and get along with on the majority of issues.

Violently attacking a system I despise largely because of its violent domination of people who don't approve of it would be quite hypocritical. This position has been shared by every anarchocapitalist I've ever spoken to. We don't need or want violent revolution, the system will be tried in small scale on seasteads and ZEDE's, based on those results it should be apparent if it is worth taking it any further than that. No bloody revolutions necessary.

That still doesn't change the fact that you're fundamentally agreeing with the statement that refusing any alternative to the status quo is de facto support of the status quo. You just point out that some people who use that argument are crazy and want to see a bloody revolution of the proletariat.