99.9% of people have more in common with an illegal immigrant than Elon Musk. Their problems aren't caused by people arriving in small boats, but those arriving in private jets.
People who have things in common, even people who’d be best friends, even those who are best friends, can compete for resources and cause problems just by existing.
Like, extreme case, not enough food in zombie apocalypse scenario and you find more survivors, doesn’t matter how good those people are it’s a problem that they’re part of the group.
It doesn’t mean the people are enemies, just that their presence is a problem.
Now, it’s probably the case that they should be allowed to move from country to country because otherwise you don’t have competition between countries to attract people. People need to be able to choose their associations in order to be free, and people should be able to move countries.
It’s a free market in that sense, and the suffering of people whose home country’s resources are strained by immigration isn’t as powerful as the suffering these people are leaving to come here, and when those two levels equalize the immigration pressure will stop. People will be going the other direction just as much.
And I think that’s all totally fair. I think people should be able to vote with their feet and go wherever is best for them.
But then being similar or dissimilar, good or bad, none of that is necessary for it to create simple resource competition problems.
All of this would be valid if we were lacking the resources to support our current population, and if every person consumed an equal amount. Unfortunately, certain people (i.e. the mega-rich and more generally Americans) are consuming resources at an unfair and unsustainable rate. You're suggesting that scarcity is the natural result of immigration and population. In a vacuum that's reasonable, but in real life we have a small number of people sucking up exponentially more than the rest.