The most important arguments for Social Security privatization are moral, not economic. Privatization would not be justifiable if it were economically beneficial but morally suspect.
However, a privatized Social Security system meets moral criteria far better than does our current, bankrupt, pay-as-you-go system. A privatized Social Security system gives individuals more freedom to run their lives, is fairer, provides more security, and creates less antagonism between generations, fostering a greater sense of community.
In fact, privatization is defensible not only from the classical 1iberal or libertarian perspective, based on maximizing individual choice and liberty, but from virtually every perspective in political philosophy. Egalitarians, who frame their arguments in terms of fairness, welfare theorists who frame their arguments in terms of economic security, communitarians who frame their arguments in terms of community, and anyone who frames an argument in terms of whether average citizens understand the institutions or programs which they are asked to support, should all support privatization.