Their skin colour is irrelevant and doesn't need mentioning, what's wrong with saying immigrants? You know full well that mentioning the skin colour makes it seem relevant, which we know it isn't. It's just race-baiting.
When Europeans migrated to America in the last millennium, I'd imagine the indigenous people had exactly the same complaints. People who move into a new area are almost always hated by those who already live there, it's a natural consequence of fear and tribalism.
The problem with immigration is a lack of integration. And this cuts both ways. Immigrants often fail to integrate fully, which leads to issues, but there is likewise often a failure on the part of the natives to be all that welcoming and hospitable, which doesn't exactly give much incentive to integrate. The problems stemming from immigration are just as much the fault of the natives as they are the fault of the immigrants. Learning to accept this makes life a lot more peaceful and will allow the issues to be solved a lot more quickly and smoothly.
When immigrants see threads like this, you can't exactly blame them for not wanting to integrate. How would you feel if the boot was on the other foot?