Uh. Well. Two things. a) Of course the police should defend itself when assaulted, I agree with you on that; but it is often in the privilegued position of power, and the police should take that into consideration, and I'm not sure how much they do. And b) aggression control does not only translate into the actual weapon used. It's actually quite irrelevant. Any kind of threat with a weapon may cause aggression in the threatened. Therefore it might be beneficial simply to delay the use of firearms longer than these police do; all scandals are seemingly because the police is way too trigger happy. It also translates into a particular attitude when talking to a suspect.
I have been stopped by police twice in my life; first they thought I had been robbing some house or was carrying something illegal (I was walking with a huge cardboard crate at 3 am, long story: it was M:tG cards) and second I trespassed into a park where I was not allowed to be at that hour, I crossed a fence. None of those events are particularly aggressive, but I can easily imagine the first instance having gone differently if I wasn't a white Dane. The police in my situation simply asked what I had in my crate, and I told them and showed them outright.
If I was a black American, with knowledge of how often blacks are shot by police, I have no idea how I would have acted. First, their interrogation could be wildly different. They could have held me down outright or keep me at gunpoint in order to investigate the crate for themselves. If so, I would need to look as unthreatening as possible, and I have no idea how to do that. If the crate contained delicates, I would need to put it down gently, and telling them back that I had to be slow could seem suspicious or provoke aggression. Or, well, they could have simply asked like they did in my position; yet I wouldn't know whether to walk up to them in order to show my crate; this can easily be interpreted as aggressive behavior, provoking them to "control" my behavior. Now, I may just be paranoid but the point is that there are plenty of steps I, being inspected, could do something wrong when I know I'm actually looking aggressive/suspicious already because of my skin color. I might especially act aggressively if I feared they'd shoot me, as I wouldn't know how to behave in order to make them not do that.
It's up to the police to get the education necessary to control these. There is no excuse for them to screw it up and be threatening on my life when interrogating.
But understand, I am not disagreeing with you that the police must defend itself when threatened by gunfire. But it's up to them to better interpret when to threaten with fire and when to actually open fire; none of these positions should be the default when controlling the behavior of a suspect.