I don't know anyone who thinks the rate at which black people kill each other isn't a problem. The thing that people like you can't seem to (or, let's be honest, simply choose not to) understand is that, in regards to the discussion of holding law enforcement accountable when they break the law, it's nothing but a red herring. But let's pretend for a minute (though make no mistake, pretending is what we'd be doing) that it is relevant (it isn't) to the discussion we're having in this thread.
The biggest difference in the two is that when a black person kills another black person, they're held accountable (they go to jail). When a cop kills a civilian (regardless of their skin color), they are rarely held accountable (they get a paid vacation). As far as I'm concerned, the rate at which cops kill civilians isn't nearly as big of a problem as the fact that, when they do it, there is almost never any consequences.