It’s not excessive force to respond to deadly force with deadly force. That is called “commensurate force”.
If you don’t know these things, then you are ignorant on the topic that you are opining about.
Where I work, we have to have a lethal force option available if a non-lethal/less lethal force is deployed.
Fact of the matter, very simply, I have seen situations where a taser was ineffective. I have also situations where pepperball was ineffective.
In training, I have seen a subject with a rubber knife stab an individual before he can get his sim gun deployed, from a lot further away than 21 feet.