The argument of the net gain is flawed. A hallmark of modern, free societies is that it's exactly not one for all, but the right and freedom of the individuum.
In all societies at all times there is some system to act against the interest of some people under some conditions. That is trivial. What differentiates modern free societies, then?
Modern free societies are characterized by a system of law that not only the weak must obey, but also the powerful. Everbodies basic rights are protected, even against the government.
Sure, we pay taxes, and cooperate by compromise in countless ways. However, that's not what we are talking about here, at all!
There is simply no way a government can lawfully kill a citizen to help some others, at least not in the EU, whatever the net gain may. That is just one obvious example of how the argument of the net gain is simply overruled by modern principles of basic human rights.
And I picked the example of beating someone up not totally at random, people went to court against the MI5 and MI6 because of their involvement with deportation of British citizens to Guantanamo [1] which may or may not turn out to be a worse fate than getting beaten up in a dark alley.
And last but not least, the licence to kill [2] seems to be an actual thing.
[1] http://humanrights.ucdavis.edu/projects/the-guantanamo-testi...
Doesn't necessarily make a society good (aka righteous).