That is a great question. The injustice was that his leg was bitten off by a whale. But the perfectly valid rejoinder would be "well that's just an event, not an injustice, as it was done by a non-moral creature because a whale can't be moral". But that is exactly why Moby-Dick's is so unique: the "bad guy" in the novel is not a human, but the universe itself. A tragic event happened to Ahab and bears resentment against a universe that allows it. Ahab seeks not to defeat man, but nature (and one could say by extension the Creator).
Why yes, that's the point. It is a tragic tale of hubris, but one of much more existential depth than what teachers will simply label as "Ahab is the bad guy".
