I get that people are uncomfortable with explicit quantification of stuff like this, but removing the explicitness doesn't remove the quantification, it just makes it implicit. If, say, we allow people to drive cars even though car accidents kill n people each year, then we are implicitly quantifying that the value of the extra productivity society gets by being able to get places quickly in a car is worth the deaths of those people.
In your example, if terrorists were the only people killing people in the US, and police (a) were the only means of stopping them, and (b) did not benefit society in any other way, the equation would be simple: get rid of the police. There wouldn't need to be any value judgements, because everything cancels out. But in practice it's not that easy, since the vast majority of killings in the US occur at the hands of people who are neither police nor terrorists, and police play a role in reducing those killings too.
I get that people are uncomfortable with explicit quantification of stuff like this, but removing the explicitness doesn't remove the quantification, it just makes it implicit. If, say, we allow people to drive cars even though car accidents kill n people each year, then we are implicitly quantifying that the value of the extra productivity society gets by being able to get places quickly in a car is worth the deaths of those people.
In your example, if terrorists were the only people killing people in the US, and police (a) were the only means of stopping them, and (b) did not benefit society in any other way, the equation would be simple: get rid of the police. There wouldn't need to be any value judgements, because everything cancels out. But in practice it's not that easy, since the vast majority of killings in the US occur at the hands of people who are neither police nor terrorists, and police play a role in reducing those killings too.