Government means authority. Authority means rules coerced from above, obedience mandatory. Doesn't matter if the government is so-called "democratic" or "Communist", obedience necessarily implies punishment to infractors. Punishment entails a punishing force. Thus government means police.
The anarchist position is, if you need armed goons to force the people to obey your rules, your rules aren't worth obeying anyway, and your system isn't worth maintaining. Attempts to produce social order by force will always result in abuse from above and transgression from below. An imposed order is no order. No police force in history has ever been succesful at what they purport to do, and there's no reason to suppose the next one will be an unprecedented exception.
The reason for this is discussed in Malatesta's theory of action: action--doing things in the world--doesn't just change the world, it changes the doer. People sometimes try to explain police by claiming it's a job that attracts bullies, but it's much worse than that. The job *is* bullying; even the most bright-eyed detective-novel reader will be transformed into an abuser when they're required to be merciless.
(because being an abuser isn't "sociopathy" or "narcissism", it's not some bad essence: it's a thing you do.)