I get what you're saying, but for what it's worth, trying to defend yourself against an unknown assailant breaking into your home in the middle of the night is rational. Firing a warning shot to establish a credible threat of violence if you happen to have a gun makes complete sense and probably the safest way to de-escalate what is an immediately dangerous situation. Because if the home assailant, if willing to engage in a firefight, was probably planning to just murder you anyway.

We should not consider the guy to have acted inappropriately.

Yes, that’s why the excuse exists. But it’s not like you can do anything to comply when the police is choking you to death.

Measured violence, yes.

In this case the guy was pointing a weapon at the police, so a killing feels justified imo.

Depends on context, obviously. The police officer has the responsibility to constantly assess the situation in order to determine if violence is warranted, as well as if that violence needs to be potentially lethal, regardless of whether or not a person is complying. As an office, one doesn't have the right to commit bodily harm, nevermind kill someone, without good cause. Hence why people talk about it so much, and also why people like to talk about police brutality even when it's regarding people that don't comply with officers (eg. protesters, bystanders, people filming, etc.)

Example: this classic https://youtu.be/7Ooa7wOKHhg. Shit like this happens in the States all the time, it's just not usually as bad, nor televised. But situations with power mad cops crop up all the time. Cops that forget that they are an arm of the law, rather than the law itself.

I don't know how the case mentioned in the article holds up though as I'm not aware of details.

The problem is that it seems to be applied inconsistently. It is a bitter joke among black Americans that the police shout "stop resisting!" whenever a racist cop wants to beat up a black person. We don't hear of nearly as many such incidents involving white people.