You can separate the two issues and that's what they're doing. Solving the bad cop activity, aka killing citizens, would be a giant step forward for society as a whole. Why can't we start with the people that are supposed to uphold the law and are basically in charge of everyone, since they answer to no one?
I'd say that should be way easier than getting criminals to obey the law, because they generally don't. I mean, this shouldn't be that confusing right?
You sound as if you think the cops go into these communities looking to kill people for the hell of it. Of course it might help the cops if the vast majority of crime wasn't committed in very concentrated areas. You think you might have a quick trigger or a negative outlook on life in general if your beat was essentially a war zone?