Nations demonstrably are suffering, though. You may make arguments about what you think is/isn't part of the core issue (economy, jobs, welfare, cultural displacement, crime, xenophobia, etc), but the result is simply observable in hundreds of millions of voices.
I am not a free market absolutist - I don't think I implied that anywhere.
That's a vibe, not an argument. And the data doesn’t line up with your catastrophe story. Migration tends to raise global output and, on average, has positive effects on destination GDP per capita over time[0]. It turns out that immigrant effects on native jobs is near net zero, as there are small losses or gains depending on skill mix in the various local labour markets. Actually new immigrants have a greater effect on the jobs of old immigrants[1] (news to me, but makes sense). Similarly in welfare, there's pretty much negligible impact in more advanced economies, leaning positive over time especially when immigrants arrive as working-age adults, which is the norm[2].
I could go on, but I think that's enough research out of me. You don't have to be a "free market absolutist" to see that the reality is far more mixed than “nations are suffering.” Yes, poorly designed immigration policies can lead to problems. No, there's nothing authoritative to backup claims that immigration is broadly destructive, which makes those voices uninformed. Or prejudiced.
I am not a free market absolutist - I don't think I implied that anywhere.