How? Simple. They both fall apart as soon as they meet Humans.
The false assumption underlying all collectivist beliefs is that Men will willingly give up their own desires for the good of other Men.
The false assumption of all anarchist beliefs is that Men will willingly not seek power over other Men.
The fundamental flaw with both is this: There are only two kinds of people; those who believe individuals must be controlled, and those who do not.
And this is why these systems (which I shall call Utopian) are doomed to fail. Men cannot be perfected. If you are a Christian, you believe that all Men are fallen. If you’re like me, you believe that MPAI (Most People Are Idiots). In fact, if you’re anything but a Utopian, you believe in the maxim “Power corrupts.” But no utopian system can ever bridge the fundamental gap between people.
Functionally, there is no difference between an all-powerful central government and no government at all. In either case, the weak are completely at the mercy of the strong, and there are no fundamental rights at all.
Thus, we have the Constitution; a document that was crafted by men who were wise enough to understand that Men respond to incentives. A document that enshrines at once the competing needs to limit the powerful and to protect the weak. Through sloth, we have allowed the original concept to become corrupted, and we have ceded too much of our individual liberty to bureaucracies because it’s easier than actually being in control. But solace will be found neither in collectivism nor in anarchy.
Only by dismantling the bureaucratic state we have allowed to come about can we ever hope to return to a properly free society.