...about this (followed up here). I say "mostly" because you could interpret what he says as saying that, while greater wealth and social freedom matter, from a libertarian perspective we have to define 'freedom' narrowly.
I see some merit to this argument, in so far as it's a response to the left, who, in the name of "freedom" encourage more and more government intervention, which often just benefits some at the expense of others, or worse. Still, though, I'd have to come down on the side that says that we should understand freedom broadly, and that, by such a conception, most people, certainly women, are more free than they were in 1880.
It's possible to make the case that freedom from oppressive social pressure is essential to a robust freedom, but that, in order to preserve other essential liberties, we're better off respecting freedom of speech and association in the law. At the same time, it's consistent with libertarian principles to act as a private citizen to influence the culture to make it more tolerant (indeed, my libertarian principles push me to do so). I suppose many libertarians won't go for this stance, but I also suspect, ala Will Wilkinson, that there are a lot of people with basically libertarian sensibilities who are turned off by the more conservative, rightish flavor of current "mainstream" libertarianism. As Caplan always says, truth comes first, but I'd suggest my take is closer to the truth.
P.S. I suppose Caplan could also agree with me on this- and I'm misunderstanding his point. He may just be talking about libertarian as a political agenda, and that a more limited negative rights conception of liberty is what fits into that agenda. I suppose that would make sense, though he seems to be talking about a broader, more philosophical libertarianism.
P.P.S. This makes me think about how we think about rights. I think it's only productive to think of rights in a narrow, institutional sense. That is, right are that which will maximize human flourishing if states recognize them as rights and act in the way that states normally do to protect rights (is that just obvious?). There are plenty of things that I consider essential to human flourishing, and I'd be pretty content to call them "rights" in a broad moral sense, but which we shouldn't try to enforce as institutionalized rights. In addition to freedom from certain kinds of social pressure, I'd also include a sense of one's life having meaning, and many others. Other things simply seem impossible to guarantee in a non-arbitrary way- health care comes to mind (How much health care are we entitled to? I haven't heard a satisfactory answer so far). Part of the problem is that people think of rights in terms of absolutes. But scarcity exists, so we have to think about how to allocate scarce resources at the margin to solve real problems. There is such a thing as devoting too many resources to protecting essential rights.