Because it's harder to pick and choose trial evidence that exonerates the cops of their malfeasance unless you have something evidencing that they told them to stop before they fired their gun, regardless of whether they actually said it before firing their gun.
I don't think in general the ACAB crowd means "no police". It means better training, independent oversight, and a division of roles (e.g. social work, welfare check).
Basically actually having accountability would go a long way towards weeding out the root problem
That’s because there is no such thing as a unified “ACAB crowd.” It’s turned into a catch-all used by people from full on abolitionists to liberals upset over specific events. In reality, ACAB is an abolitionist phrase. If all cops are bastards, the entire concept of policing as we know it is flawed and needs to be done away with.
That’s the problem with catchy phrases spreading over the internet: they lose all meaning.