interacting with a shoplifter or drunk driver and start bellowing “BLACK LIVES MATTER!”
I'm struggling to see this in a manner that doesn't read as racism. It shouldn't be socially unacceptable to insist that black lives matter, particularly towards one of the organizations most prone to abusing them. It's also telling that those were the example crimes you cited and that, regardless of the accused infraction, that still shouldn't imply that their lives therefore don't matter.
And the reason for the mindset that ACAB is because if they weren't, they wouldn't be cops. There's countless examples of "the good ones" being run out departments (or worse), meaning that any remaining are either active participants in corruption and/or abuse, or at least willing to look the other way to it. It doesn't matter what an individual's ethics are if they allow themselves to assist others in harmful activities.
The mythical good police should be furious at the reputation their bad members have brought to the profession and be taking loud and decisive steps to reform. But there's not large numbers of precincts striking (or similar) over the human rights abuses, except for their desire to continue causing them without consequences.
Entirely hypothetical situation, but a passerby seeing police mistreat a black suspected drunk driver physically or verbally is an appropriate and useful time to make the point. Even if everything appears above-board, if the cops aren't doing anything wrong then they shouldn't be concerned with being reminded to treat others' lives with respect, right? Part of their job and training revolves around conflict resolution and dealing with frustrating situations. They should be able to handle people shouting things at them.
I'm not trying to get into a lengthy discussion over police abuse or their current role in our society either. But I generally think until their accountability is the norm and not the exception they deserve all the animosity coming their way. If they want to lump everyone into good guys and bad guys without caring about nuance then the same can be done for their group.
I'm also not going to pick apart all the things in your links but I strongly disagree with your recommendations about interacting with the police. You also spend a lot of energy trying to equate fewer headline police abuses with effective and thorough widespread reform.
[This section is more directed at others reading the thread than expecting/inviting a retort]
You flat out do not talk to them in any capacity beyond the hard legal requirements unless you've talked to a lawyer or someone educated and qualified enough to give sound legal advice. Your saying things like "don't refuse to give ID" or "Just talk with them. Tell them what you know, help them figure out the situation." as a blanket suggestion can potentially be harmful to an entirely unrelated and innocent individual. I wholeheartedly wish this wasn't the case. I'm an overly honest person and generally believe that telling the truth and providing whatever help you can in a given scenario is the correct course of action - but with the current police and legal situation in the US there's only the potential to cause harm to you or others if you give them the benefit of doubt and volunteer information. It's not just for the protection of stoners and crime-adjacent people, "proper upstanding citizens" have found themselves as people of interest in a crime they were either a victim of or unconnected to because they wanted to tell their side or offer what little they know about the event. And playing dumb with ICE has the potential to bite your ass if they decide to try proving you were impeding an investigation by providing false information or downplaying your knowledge; it's safer to state you're invoking your right to silence and then say nothing at all.
I've had interactions with police where I've talked to them and nothing bad has happened to me, but I'm not going to try telling others that's the smart or correct thing to do. And just because I got an empty chamber doesn't mean playing Russian Roulette is safe. In this poor analogy it should also be recognized that my game might be different than someone else in that my revolver is aimed at an extremity, while theirs is aimed at their head with more chambers and only one being empty. Instead of talking about tricks to determine if the cylinder landed on a safe spot the more prudent advice is just don't play the game at all.