RE: “they insist that social justice ought to be part of libertarianism but are unwilling to tell us what it means.”
Thats right. They have no program, no argument, no artifice. Only a sentiment. This is why they’ll fail.
But libertarianism, or at least propertarian reasoning within libertarianism, provides the solution to ‘social justice’ — if that term has any meaning other than ‘redistribution’. The solution arises from insight is that the ethic of voluntary exchange does not require unanimity of belief in anything. It only requires institutions that provide a means by which we can construct exchanges between groups that are not possible to construct by alternative means due to pervasive ‘cheating’. Cheating which is expressed as competition, is beneficial in a market for consumer goods, but a form of privatization or corruption when applied to infrastructure or services (commons). Institutions are necessary for creating those exchanges free of ‘cheating’– private appropriation of common investments.
The problem for us lies in constructing the institutions that allow exchanges between groups. Even assuming representative government is a good, if for no other purpose than to divide the labor of decision making, the classical liberal model of multi-class government should have been expanded and reinforced so that classes could conduct exchanges, most of which are inter-temporal borrowings from one another. Instead we undermined that feature of the classical liberal government with fully democratic solutions disconnected from the material differences in interests in the population.
Furthermore, institutions of all forms are under attack by ideological libertarians. Rothbardian Anarchism has stolen the libertarian movement. But, we don’t need to give up on institutions. We need to give up on creating institutions that depend on a unanimity of belief in ends, means and virtues. A requirement that does not pass the most casual scrutiny.
Most ‘justice’ is simply accounting for and settlement of differences in production cycles. There is no reason we cannot bring forward to the disadvantaged the benefits of the difference in production cycles between the classes, in the same way we bring forward productivity through borrowing and interest between capitalists and entrepreneurs.
There is no reason that is, other than we lack the political institutions to accomplish in politics what we accomplish daily in banking as a matter of course.
That’s the answer to bleeding heart libertarianism: institutions.
But we have to understand Rotbardianism as all but a prohibition on organization first.