How to de-platform them:
If there is an unrestricted flow of goods and people across the borders, then there is no law. If there is no law, there is no need for politicians. There is no need for party. There is no need for voting. There is no need for DEMOCRACY.
Libertarians don’t want any laws. They want every man for himself and every decisions completely local, communal actually. Of course there are many flavors of libertarianism, from pure anarchists to veering into some kind of anarcho-communist. They try to put normal face on it but once you dig a bit, you see the crazed utopian hell that it would be.