Not being a murderer, regardless of the utilitarian pay-offs is an important part of people's identify and reasoning about morality.
It is fascinating just how damn crushing such tags can get once you start multiplying them. Even in the eyes of other people. Consider someone who has killed for the greater good. Now consider someone who has killed, raped and pillaged for the greater good (by historical standards this is the regular war hero pack).
Now consider someone who has killed, raped, blackmailed and tortured for the greater good. One may be glad that such people do exist and that they are on ones "side". But wouldn't you feel uneasy around such a person? Especially if you couldn't abstract away their acts but had to watch say videos of them being performed.
Imagine carrying those memories, what is your self-conception? The only tale of virtue you have left when you are alone at night is that you posses the virtue of being the kind of person who is capable of suspending moral inhibitions based on long chains of reasoning. Maybe you are just that good at reasoning. Maybe.
Now consider someone who has killed, raped and pillaged for the greater good (by historical standards this is the regular war hero pack).
The parenthetical is true but the raping and (for most part) the pillaging was for personal gain, not the public good. It takes much more effort to contrive scenarios with folks who "rape for the public good".
If it's worth saying, but not worth its own post, even in Discussion, it goes here.