Injustice for the common good

Over at Front Porch Republic, Walter A. McDougall has written a two part essay on, for lack of a better description, the history and future of conservatism in America. While the entire piece is worth reading, one part stands out in particular:

In every era America’s leaders, the ones inventing everyone’s future, evinced the qualities of the hustler and dodger, finding ways around obstacles to change and growth whether or not they conformed to ethics and laws. Whenever such corruption was perceived as damaging to society and of benefit only to the hustler, then American public opinion damned it and demanded the guilty be scourged. But more often the great scams in American politics and business, from the Transcontinental Railroad to urban machines, could be perceived as socially beneficial, for instance by opening up new opportunities for the many or keeping immigrants under control. In those cases Americans winked at the means employed to pursue the ends, or else applauded the authors of creative corruption, just as their colonial forbears had smuggled, cooked the books, and rioted against customs agents and Redcoats rather than obey the Navigation Acts.

McDugall appears to consider this a particularly American trait. However, it is nothing new. After all, it’s the same defense of injustice that Thrasymachus made in The Republic:

If someone commits only one part of injustice and is caught, he’s punished and greatly reproached—such partly unjust people are called temple robbers, kidnappers, housebreakers, robbers, and thieves when they commit these crimes.  But when someone, in addition to appropriating their possessions, kidnaps and enslaves the citizens as well, instead of these shameful names he is called happy and blessed, not only by the citizens themselves, but by all who learn that he has done the whole of injustice. … injustice, if it is on a large enough scale, is stronger, freer, and more masterly than justice (Plato, Republic, 344b-c).

Plato, of course, disagreed with Thrasymachus and argued that justice was more than the advantage of the stronger. However, Machiavelli later resurrected Thrasymachus in his The Prince:

it is a very natural and ordinary thing to desire to acquire, and always, when men do it who can, they will be praised or not blamed; but when they cannot, and wish to do it anyway, here lie the error and the blame. (Machiavelli, p. 14)

and 

if he wants to maintain himself, to learn to be able not to be good, and to use this and not use it according to necessity. (Machiavelli, 61)

So how should we deal with injustices that actually promote the common good? It’s easy to adopt a results-oriented critique, but doesn’t a proper application of justice require more?