Who is saying these things? Mass migrations are a material fact and part of human society and evolution. Also Europeans conquered and settled America, no way you can give that shit "back to the natives."
Fucking where exactly? Don't say USA or Brazil
I'm pretty sure most leftists support Palestine, Catalonia, and da Kurds. Not to mention the leftist separatist movements like the IRA and Basque movements.
So, Is Varg just an an-com in denial, or what?
I personally don't think that this is inherently incompatible with leftist thought, given the right circumstances - specifically, the circumstances of complete worldwide socialism. If your material circumstances are provided for equally no matter where you are in the world, most people are not going to choose to emigrate. That is a conclusion I'm surprised more Zig Forums people haven't come to, you'd think they would all be pushing for socialism for precisely that reason.
All that said, I think that people should obviously be able to live wherever they want, and would vehemently oppose any restrictions set by the state, again, given the theoretical conditions of worldwide socialism.
It won't really exist if people actually have no reason to leave their homeland (you know, because there's no risk in staying there). As for it being (presumably a necessary) part of evolution? How the fuck did things that were the same species eventually evolve so differently simply because of where they live? That's something for you to research.
SAYS WHO?
Hm… Maybe an area on Earth that becomes habitable soon after our technological advancement increases enough to make it livable (becomes communism allows technological advancement more than capitalism does), like an underground city in the arctic circle or something.
Basically all of this is true. We don't need state restrictions to stop migration. We just have to make people happy wherever they live.