Nostromo is groping here for the freedom to steal by right, or rather to efface the very notion of property, as utopian socialism promises. As soon as he finds no condemnation for acting as a "thief," he turns around and offers a cascading series of justifications: first, that the rich deserve to be stolen from, since their entire fortune is "stolen from the people"; second, that in fact no theft has taken place at all, since they "lost" the silver through folly; third, that they deserved to lose it because they "betrayed" and "deceived" him. Note that in addition to the silver, the thing he has taken from the rich -- the thing they have lost through their folly and betrayal -- is himself, the allegiance of the People.