But why are they against mass migration? It almost always has to do with the culture of the current immigrants being different from the one of the host country.

But why are they against mass migration? It almost always has to do with the culture of the current immigrants being different from the one of the host country. >As for the market place of ideas, the first problem is that converting people is a slow process and can take many generations. The process can even go backward at times depending on socio economic factors. The other issue is that if you have enough migrants in sufficient concentration then they can build a society within a society, almost entirely cut off from that market place. So in your mind, the marketplace is not sufficient enough on its own and requires regulations? That's very much not a liberal philosophical principle. It's a rejection of the lassiez-faire approach to speech and ideas which the liberal philosophers championed. The things you mention apply to all humans, not just migrants. If for example the Universe is heliocentric but the geocentric believers are in sufficient concentration they too can just build a society within the society and shield themselves from the heliocentric people, right? Why did that not happen? The reason is that migrants cannot realistically avoid all the ideas of the host country while living there. It's not possible. You cannot cut yourself off from a market you live in.