This is the problem though, you have any frank discussion on conduct and it falls back to people's feelings. You can't let people's feelings get in the way of making tough decisions. They are going to be viewed as the enemy all the time their members keep shooting or murdering black people. There needs to be culture change from top to bottom and they need to get on board with it. Those officers who can't or won't need to be removed.
TBF there needs to be a lot more than just culture change.
There needs to be an independent (of the police and of politics) means of investigating deaths, of all kinds - our coroners system is not perfect but its light years ahead of anything they have (which is crazy given that its medieval in origin). Once they have that, it needs to be able to deal with and be seen to deal with people who kill others without justification.
There needs to be fewer but much larger agencies, probably one per state rather than the myriad of forces that currently exist. Bigger forces usually mean better training, more professional cops, more cops per person (which is important as it means less of them are on single patrol and so less likely to go for the gun first), more capability to deal with major crimes and public order properly and more actual accountability rather than the farce that is voting for a sheriff. Having a national register of cops as well would make it more difficult for officers to mess up in one force and make it somewhere else (which is something the UK isn't immune to as seen with the PC that pushed Tomlinson).
Finally there needs to be a real look at what their police are actually for. Over here, we have
the principles established by Peel that, by and large, our police have always operated by. Cops and especially police staff are, even in London, usually recruited from the same area they are going to cover and have an interest in it being done properly. Senior cops will invariably try to build and promote community cohesion and cooperation (even if idiot politicians do their best to undermine this), with the result that for the vast majority of the time there are no no-go zones anywhere in the country.