People move through the streets in the millions, and for the most part they do so without violence. It’s not as though every single one of them is held back by fear of the police. Sometimes it’s simply the case that a person, on a very human level, cannot be bothered to harm another when they could just as easily refrain.
More broadly, I find the idea that human beings require—and will always require—top-down control deeply unconvincing. If we truly believe that people are so fundamentally incapable that they must be disciplined indefinitely, then so be it—let the heavens burn. But if we do not believe that, then it seems only natural to orient ourselves toward a trajectory of development that allows for greater, not lesser, degrees of individual and collective freedom.
In that case, the question is no longer “anarchy or not,” but rather: when anarchy, what kind of anarchy, and by what means do we get there? These are altogether different questions—and they are open to discussion.

I disagree that it requires a posconventional level of moral development. People strongly lean to match and reflect behaviors of others rather than invent their own, which is shown by various experiments. Defecting is a rational strategy, but we're irrational beings first (or rather überrational, with the same flavor as in "supernatural"). And our ethics emerges from our aesthetical principles, rather than on our intellectual decisions, because it's intimately tied to subjective experience of suffering. Aesthetics, in return, is largely shaped by familiarity. So, I think it's not a problem of "uplifting humanity to moral heights", but rather a question of normalizing cooperation in a society. After all, monkey see – monkey do.

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