guess you have a libertarian nation with open borders
how can this libertarian nation survive tribalism and ethnic networking by a group that is very hostile to the libertarian majority, and that has somehow managed to convince the same libertarian majority that tribalism to their favor is morally evil?
for the hostile group it may be very easy to gang on each libertarian individual to take them off their way one by one until an oppressive state has been established
imagine this hostile group importing millions of semi-slaves from highly socialist countries, keeping them inside of the libertarian nation with minimal inversion, i.e. making them sleep in little rooms, minimal food provisions
and imagine they manage to convince the semi-slaves that their lives would be far better, if only the libertarian majority could share some of their wealth. Now the hostile group arms the semi-slaves with all kind of war weapons and waits until the numbers are finally in their favor to launch an all-out statist revolution
what kind of measures you would take to avoid this problem?
Imagine that you have closed borders, but the hostile group and the semislaves are already inside the country