The essay simply explains one core tenant of anarchism: that humans rely on cooperation and trust on a core fundamental level in everyday situations, even in capitalism. Societal structures collapse once that base-level of cooperation doesn’t exist.
Because people who will not cooperate may be rare, but they are not vanishingly rare. They are common enough that we need explicit rules backed by the violence of the State to enforce them. Everyone knows this at a base level too. That loud neighbor. That guy flipping you off in traffic. The woman at the store eyeing the jewelry case a little too hard. If we didn't have laws, and cops to enforce them, these people would do what they wanted regardless of what anyone else wanted.
Which leads to the follow-up bullshit of "if you just destroy the protective power of the State, all the bad people will actually be good people!" Yeah and rainbows shoot out my ass when I fart, too.