I think it's perfectly reasonable to take a non-absolute position here. You can want a somewhat functioning, somewhat effective police force, but not one that is more functioning or effective than the one we have in reality; or, in fact, you can want one that is less functioning and effective than the one we have now, without being completely dysfunctional and ineffective.

(One could imagine a police force that is effective enough to stop murderers, but not effective enough to stop dissidents. Such a police force would be more useful for a society that wants no murder than for one that wants no dissent.)