To commit most crimes you have to be thinking badly and acting badly, that is true of serious crimes for sure.
If you are threatened with deadly force, or force that would reasonably cause bodily harm, and you protect yourself you are not thinking nor acting badly. You are justified in what you are doing. And the force you are threatened with does not have to come from a weapon.
The guy that got shot in Charleston SC and the guy selling cigarettes that died from the chokehold were not justifiable homicides (although in the second case the jury wrongly, in my opinion, acquitted the police).
These cases are not the same. To say they are isn't just comparing apples to oranges its comparing apples to cinderblocks.