Contrary to popular assertions, Ancapistan is a real place and is conventionally referred to as prison. In all seriousness, I have been living in the US federal prison system for four years now, and in many ways, prison society actually is fairly anarchic. Considering these societies (plural because prison culture is heterogeneous across geography and across institutions’ security levels) seriously should dispel any notions of humanity that could be categorized as Hobbesian pessimism.
One obvious way in which prison is libertarian is the inability to utilize the state’s traditional method of sending people to prison as a form of punishment, given that prisoners are already in prison. More generally, however, at the facility in which I reside the institution staff