He did not rationalize unfairness.  He said that if employers actually are paying women less for the same work, we would expect profit oriented companies to hire more women than men.  Companies are out to make profits for shareholders and reinvestment.  If they can get the same work for less pay by hiring women they would be highly motivated to hire women rather than men.  You see this is the profound contradiction in the notion that women are paid less then men for the same work.  I suspect that the reality of the situation is that those who do the wage surveys view "same work" quite liberally and in reality if one really stuck to exactly the same job function much of the wage disparity would disappear.