The "if it saves on life" cliche is more aptly aimed at broadly applied laws that don't accomplish what they are supposed to accomplish. The whole concentrating on "assault weapons" while the vast majority of murders are not from scary guns.
But in the Fabrikant case, which I believe bross is referring to, people knew that guy was unstable and making threats. I assure you, if I had been one of those people I would have cared very much if something could have been done and "saving one life" by an action would have been very appropriate!