As fascinated as I am I would double check that I have something to row with if I take a motorboat out to see the island from afar. No way in hell I'd want to step foot on that island or be at bow and arrow distance.
Their first major contact with the outside world was in 1880, when a British colonial administrator kidnapped six of the Sentinelese, two of whom died from disease before they could be returned - and who knows what diseases the other four brought back with them when the British dumped them back on the island.
Non-human animals regularly kill outsiders that have made incursions into their territory. Chimps for example will even 'invade' neighboring territory and attack to try and grow their territory.
Male elephant seals will attempt to kill other males that are 'sneakers' that attempt to reproduce with their harem.
'violent xenophobia' is instinctual, humans however try to rise above this in many societies but in primitive cultures outsiders represent uncertainty at best.
Can you prove that?
The closest I can think of is Texas, but even there you'd have to meet the definition of "criminal mischief at night".
in which US states can you legally use deadly force against anyone on your property (not in your house) without being threatened?
Yikes, that doesn't sound right. Citation please?
A fish has no concept of water, it doesn't know it is in water, it doesn't know there can be existence outside of water, and it doesn't know it depends on water. You cannot possibly deem the culture extreme & violent when it is much like fish, that doesn't know of alternatives.
Most of all, fish will defend themselves against perceived existential threats - fish aren't xenophobic to defend themselves against sharks
Does that not invalidate your argument?
Animals of all types also exhibit xenophobia, even the ones that have "no hint of modern civilization".