How is defending against an invasion not legitimate?

The modern population of the island are the natives, kinda like how Icelands population is completely native to the island. Not to say people didn't fuck around on the island occasionally but there's basically no evidence of prehistoric settlement of the Falklands.

Sure, I entirely agree on principle. But that's my question, who are these people? According to Wikipedia, there are no such people:

Although Fuegians from Patagonia may have visited the Falkland Islands in prehistoric times, the islands were uninhabited when Europeans first explored them.

So I suppose I have my answer overall. The people living there are broadly the descendents of the French, Spanich and English who settled there in the late 18th century. The French ceded the settlement to Spain a year after they started, so even just scratching the surface of the situation it looks like it's been a mess for 250 years.

But in any case, the people living there, now, clearly want to remain a UK territory.

Greenland wants to be part of the UK 🤔

Malvinas not Maldives (they're half a world apart), and there have been briefly Spanish/Argentinian populations on the islands between 1774 and 1820 but none since then. The majority of whom were one of a) a military garrison b) convicts c) guards of convicts. Very small numbers of non military settlers during that period

So broadly yes, everyone who has been there since the early 1800s is aligned with the UK