Me going to the US illegally today should not be acceptable. I should need a VISA. Cos I'd be an economic illegal migrant. Not necessarily trouble but consuming resources and opportunities that American parents worked hard to provide for their kids.
Someone from a war zone should (you'd think) have to make some petition for asylum. Where and how I've no clue but there should be a process.
It's all about scale though I'd expect.
If a 20 immigrants came ashore on a small boat in Kinsale after fleeing Yemen in sure the locals and the government would be pretty welcoming. If 200 came over the following weeks it'd be a different story until eventually they'd not be welcomed at all. Somewhere in between a fair process would be needed.