Reference to 'economic injustice' is weak without identification of the morally relevant facts. For me the question is whether economic injustice (positively construed) is characterized by one group systematically winning asymmetric zero-sum games (or strategically equivalent games, meaning those whose payoffs differ by a positive affine transformation). This provides strictly more information than vague reference to "economic injustice", which can be dismissed as a normative judgment.
Whether the characterization holds is an empirical question. Whether one ought to condone the systematic winning of asymmetric zero-sum games is a further question. It is in my view rhetorically important not to cede the "value neutral" conceit of (many practitioners of) economics to conservatives. Unfortunately many non-conservatives seem to lack the economic and mathematical background (not to mention imagination--pardon the paralipsis) to turn the "value neutral" conceit on its head. The term "economic injustice" could stand further refinement by explicit mention of its positive, game-theoretic aspects. That involves characterizing, in game-theoretic terms, economic phenomena that game theorists and economists have chosen, for various reasons, not to study.
A philosophical attitude isn't particularly helpful here, if this means the unfortunate Anglophone tendency to limit philosophy to "patrolling the border between sense and nonsense." But the historical fact that game theorists have tended to study empirical questions on terms that can be addressed in game theoretic terms is not a reason to dismiss what might appear to a philosopher concerned with "conceptual analysis" as some kind of private, special language.
I don't know if morality has credibility or not. What would that mean?