An excerpt from Hoppe:
Many libertarians hold the view that all that is needed to maintain a libertarian social order is the strict enforcement of the non-aggression principle (NAP). Yet... it does not hold and apply, or rather it is insufficient, when it comes to people living in close proximity to each other, as neighbors and cohabitants of the same community.
A simple example suffices to make the point. Assume a new next-door neighbor. This neighbor does not aggress against you or your property in any way, but he is a “bad” neighbor. He is littering on his own neighboring property, turning it into a garbage heap; in the open, for you to see, he engages in ritual animal slaughter, he turns his house into a “Freudenhaus,” a bordello, with clients coming and going all day and all night long; he never offers a helping hand and never keeps any promise that he has made; or he cannot or else he refuses to speak to you in your own language. Etc., etc.. Your life is turned into a nightmare. Yet you may not use violence against him, because he has not aggressed against you. What can you do? You can shun and ostracize him. But your neighbor does not care, and in any case you alone thus ‘punishing’ him makes little if any difference to him. You have to have the communal respect and authority, or you must turn to someone who does, to persuade and convince everyone or at least most of the members of your community to do likewise and make the bad neighbor a social outcast, so as to exert enough pressure on him to sell his property and leave. (So much for the libertarians who, in addition to their “live and let live” ideal also hail the motto “respect no authority!”)
The lesson? The peaceful cohabitation of neighbors and of people in regular direct contact with each other on some territory – a tranquil, convivial social order – requires also a commonality of culture... multi-culturalism, cultural heterogeneity, cannot exist in one and the same place and territory without leading to diminishing social trust, increased tension, and ultimately the call for a “strong man” and the destruction of anything resembling a libertarian social order.
And moreover: Just as a libertarian order must always be on guard against “bad” (even if non-aggressive) neighbors by means of social ostracism, ... so, and indeed even more vigilantly so, must it be guarded against neighbors who openly advocate communism, socialism, syndicalism or democracy in any shape or form. They, in thereby posing an open threat to all private property and property owners, must not only be shunned, but they must, to use a by now somewhat famous Hoppe-meme, be “physically removed,” if need be by violence, and forced to leave for other pastures. Not to do so inevitably leads to – well, communism, socialism, syndicalism or democracy and hence, the very opposite of a libertarian social order.