No, economics is a predictive social science, not a system of moral philosophy; the rational choice model has nothing to do with how it is just and fair to treat people. It was the dominant model because despite being self-evidently not fundamentally correct (it assumes a number of things, like perfect knowledge of future outcomes, that no one believes to be literally true or even plausible) it was believed to be an approximation that would predicted results better than any alternative model available at the time, in general and in a wide array of specific cases.
