I'm not sure I'd dismiss your argument so quickly. If one considers the "just" to be the best decision, given the circumstances, then most criminals are trying to be just. They may badly need money for their family. Or perhaps to feed a drug habit (In which case, as you said, perhaps they are ignorant of what really is just.) If they didn't think it was the best decision, for some good, why would they do it?
In that case, it is a convincing argument. Consider that most dictators and despots seem to think they are in the right (Ww2, etc.) Compare this to "normal" criminals, who seem to have poor impulse control (lack of long-term planning. )
Of course, that has nothing to do with the article. I've brought up an argument and then dismissed it just as quickly :)