The problem in that story is that it wasn't just blackmail; it was a fait accompli turning in. I can see trying to negotiate with blackmailers or involving the police. Once you have been turned in, all negotiation has failed.

Understood. But retaliatory murder is neither a justifiable response or a resolution to that problem. It's simply revenge and pre-meditated murder. It convinces the general public that the common myth that we're a bunch of dangerous psychopaths is correct. Our responses and solutions to problems that do not involve violence initiated against us have to be civilized if we ever hope to win over large segments of the public, and to achieve a more civilized society. Our responses have to be commensurate with our goals.