To me it brings up an interesting ethical question. While we have no right to impose our culture on them, is it fair to not even allow their children or any succeeding generation to choose for themselves what life they get to lead? Even the Amish youth are allowed to go out into the world to see it for themselves and decide which life they will choose.
I'm with the school of thought that says that we should leave these people in peace unless they somehow reach out for help or are in such distress that there is a compelling reason for us to intervene.
Having said that, it strikes me that we have gone all the wrong ways about establishing contact.
Those making attempts seem to have been predominately male and tried to make the contact person to person.
No wonder an apparently patriarchal warrior tribe have perceived them as a threat and taken action.
If I was trying to engage with them I would start by leaving objects where they could find them and keep people well out of it.
Firstly I would leave something simple and useful that they could make sense of with a little experimentation - a wheelbarrow, for example.
Even if it took a month before someone examined it and tried it out, there is a fair chance that they would see that it posed no threat and could be handy for collecting firewood or coconuts or whatever.
Assuming that they assimilated the first article into their lives I would try a second - maybe a bicycle for them to experiment with. Or a simply musical instrument like a recorder or penny whistle.
If they became interested and looked for more such gifts, they could be slowly introduced to new concepts which might expand their horizons and make them curious rather than frightened by the world beyond their island sanctuary.
But if the avoided or destroyed the gifts, that would be a clear message too.