> I don't see how you "reform" a culture like that.
You do it through hard work on real reform at the local level, something that BLM (the organization) isn't really interested in. I don't agree with everything but the ideas outlined here https://www.joincampaignzero.org are a good start. Some communities are in much worse situation than others and I think new leadership is urgently needed in many of these places (i.e., vote for change).
The rhetoric that you are using is supremely dangerous. Look what is going on in Portland as the police and local political leadership have withdrawn from the basic goal of public safety and ensuring a peaceful, civil community. It is devolving into warring tribes. It is actually astonishing to me that it hasn't escalated further than it has but I see that this weekend things have changed a bit as some new tribes arrived resulting in brawls/skirmishes/fighting between the tribes as opposed to with police.
To advocate or even suggest that policing, as a system, is irredeemably flawed and can't be reformed is to actively invite in chaos and civil unrest. Instead of a civil police force you will end up with an ad-hoc collection of private security, thugs, violent gangs, protection rackets, and so on. Due process will not exist and whatever problems you attribute to the current system will be much, much worse in this new "system".