Once again, because I know I've sad this before in the past (And I'm speaking generally here),...
1) Just because you have a black friend, doesn't mean you're incapable of being a racist. All it truly means is that you know a black person that is willing to associate themselves with you. I personally had a good friend in high school that I immediately cut ties with when I found out he was a racist piece of crap online/in private.
2) As someone who has often been the "black friend," if you're finding that you constantly need to remind people that you have a black friend (or friends belonging to other minorities) when you give your take, there's usually a pretty good chance that your take is backwards in some regard. Also, using your "friend" as a scapegoat is frankly not cool, full-stop.
It's not a good scapegoat, and it will never be a good scapegoat. Stop using it (again, speaking in general).
BLM the movement and BLM The Organization are not always the same thing (especially currently), and it is absolutely possible to support the movement/idea without supporting the organization. This is also something that has been explained in this thread and others.
Once again, you seem to be missing the core issue, in which an officer of the law, whose job it is to also protect suspects, because even criminals have rights in this country, was completely negligent in his duty and killed a guy who was already detained and was not a threat to a single soul. And that's not to mention the decent number of cases over the past few years in which and officer killed someone unnecessarily (usually a minority), and didn't face any criminal consequences, even in the cases where there was clear-as-day footage of the incidents.
Is murder, especially random murder, bad? Yes, very.
Are unnecessary deaths caused the negligence of the people who are supposed to protect us also bad? Yes, very.
Is it possible to be mad about both? Yes, and people absolutely should be.
Are these things on the same level? Not always.
I have no idea how to make this any more clear for you.
And police brutality being part of the "real world" makes it acceptable and not worth challenging.....how, exactly?