Obviously there is more nuance than that. If police kill an active school shooter, is your response “Tsk, tsk, two wrongs don’t make a right”?

His "agenda" was exposing the crimes being committed by the United States in places like Iraq and Afghanistan. That's a completely legitimate and even noble agenda for a journalist to have.

Neither you nor the other first-order responses seem to acknowledge that the two actions are not exactly independent - it's not like the US government did a bad thing, and then Assange went and did a completely unrelated bad thing. The problem (as also hinted at in kevinventullo's response to a different subthread) is that the USG set up a situation in which anyone revealing their misdeeds would basically have to reveal the identities of the translators, or at least pay a great cost (in effort, credibility (as they no longer can release quite "original documents") and possibly liability (if the "editorialising" can be spun by lawyers somehow)) to not do so. The situation is thus a lot more similar to someone shooting the hostage (except of course in this case the hostage was not even actually shot!) along with the terrorist that took it and was threatening to blow up the building, then someone shooting a random person because they are a psychopath.