Pesky immigrants always seem to show up...
Why should they be allowed to come into your fort, sit down in your legendary dining hall, eat your buzzard meat roast, and drink your sewer brew?
They shouldn't.
Not until they've proven themselves worthy - or, more likely, died horribly. It's natural selection. Just think, you could be breeding Sarduakar dwarves.
I got tired of making beds for layabouts that run from menacing Capybaras. Beds that I could have used to make steel with...
So now I drop a pick, and maybe some leather armor (if I'm feeling especially beneficient - food.) outside my gates and run two separate little colonies. One that dies rather horribly rather regularly, but that periodically improves my defenses, and one bunch of fat survivors that sit under a mister and make pointy stuff to put outside for other dwarves to use, (and die using)
There's probably some silly ethical objection to treating, blood sacrifices, blue collar dwarves with pretensions to cheesemaking, so harshly...
I didn't invite them.
Sometimes you end up with a highly trained military this way... Make sure they die too, that's what they are for. All your nobles and first ground breakers, stay turtled up inside your impenetrable fortress, doing science projects and not worrying about silly things like armor...
Place all migrants into squads upon arrival, have them kill everything (or die trying) and put the spoils right inside your airlock to the outside. (You know for the fat inside dwarves to use.)
These outside folks are especially useful for exploring the caverns in a risk free (to inside dwarves) way. Send one dwarf down (outside your defenses) with a pick and construct a floor over the opening right after the feckless boob noble patriot starts down to meet the clowns. Why waste food, setting up a stockpile down there? If the beard finds something to eat... well, then it's lunch time and you won't have to go to the trouble sending another one down there.
Tantrum spiral? Not on the inside, they are living easy. Outside... Who cares? The fort goes on and you never have to use a single cage trap... well except to keep turkeys, pigs and dogs in.
Two colonies, or rather one colony and one death camp.
Do this successfully and you become qualified to run any Middle Eastern country.