Today I'll go a little further and suggest that justice in fiction can also be an aesthetic experience. Writing workshops tell us that the ending of a story must be both surprising and inevitable to be satisfying. That's a paradox, certainly, and it raises the possibility that paradox itself is aesthetically pleasing. Now, it might not be ethically pleasing, not in real life anyway, where we want our good folks rewarded and our evildoers punished unambiguously. Yet, that hardly ever happens. In life, the ironies--e.g. the embezzler who spends a month in jail, and then gets a book deal and his own reality show--are often maddening. However, in literature, possibly because we know we can't do anything about it, and aren't expected to, a certain kind of success-in-failure (or vice versa) feels just right. Moral ambiguity can be safely viewed as an aesthetic problem.
That in itself isn't bad; it might allow a more nuanced and less heated consideration of the issues at hand. For example, in Hound, Holmes and Watson, in their zeal to solve the case, allow their client to get killed. In real life, that would be shocking and galling; in the novel, it creates a sort of frisson, an uncanny halo around the supposedly good work of solving crimes. Part of the reader's satisfaction with the surprising/inevitable ending is that it feels real, while being explicitly unreal. Awareness of that aesthetic/ontological balance, I think, is one of the great pleasures of fiction. (There, I worked in the Hound reference.)
Which is also to say: one must resist the temptation to impose the aesthetic tenets of storytelling on real life. At that, our culture is failing miserably.