"Whether they're right or not is another issue [..]"
Morals are all about right or wrong - you can't have it both ways.
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The OPs belief is entirely objectionable. Have none of us learnt anything from history?
EDIT: Actually, maybe that wasn't quite strong enough. The OPs belief is utterly abhorrent. It's from the same school of thought that's used in attempts at 'ethnic cleansing'.
One person can't have it both ways. Two can have opposing viewpoints and still be completely, logically correct in their own eyes. It's a fundamental aspect of communication between different entities.
edit: how about a starting point (in no way intended to be snide / insulting, I'm entirely serious about this):
Murder is wrong, right? Why? Completely objectively, why?
I was referring to two (apparent) opposite points of view, and it seemed like you were using semantics to disagree. I read the last part of that sentence as you personally stating that the OP had a moral obligation, which I now realise might have been incorrect.
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I understand that people form their own moral compass, and that views differ - but sometimes, I think there are issues which are so universally felt that the whole of society has to learn how to deal with them in a united way.
There are so many examples of self-proclaimed 'superior' societies dominating and assimilating smaller cultures which aren't able to defend themselves.
Many of these examples are well documented and - now that we have the benefit of hindsight, we can see exactly what kind of effect was left behind.
I think most people can agree that gross injustices took place.
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Would you voice any objection to a holocaust denier?
Whether it's a majority opinion or not, it's hard to say. I encounter both sides very regularly, while you apparently don't. Such is life.
As to the holocaust deniers, yes, I would. Because I disagree with them, and because it's essentially an intentionally-ignorant standpoint that doesn't stand up to scrutiny.
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But as to contaminate-or-not, I do prefer contamination so they can choose. Otherwise, it seems to me we're treating them like animals in a zoo, incapable of choosing intelligently for themselves. It also implies our culture is just so virulent that any who come in contact with it are sure to lose their way, join us heathens, and destroy their culture; again, insulting their intelligence and based on what's essentially a superiority complex.
For myself, I'll always choose contamination over being walled off. Others will disagree. But until we're capable of knowing they disagree, we either force some contamination to find out or we force them behind walls, taking away their choice. I find walls to be more offensive to sentients as a whole.
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Look at what happened to Australian Aboriginals - the settlers who separated kids from their families had the best of intentions - but they also had a sense of superiority which gave them an utter contempt for the culture of the children in question.
There are some parallels between those settlers and the OP's statement:
"There is nothing good or enviable about uncivilized lifestyles to preserve; any actions that maintain them in that lifestyle are ensuring they literally die young, mostly of preventable causes."
I'm sure that regimes that take part in ethnic cleansing believe that they're doing the right thing. A sense of superiority helps them to make their choices.
Whether violence is used or not, in some ways, the effect is the same.
EDIT: If you read about these people and the problems that they're facing, it's not difficult to see that they were pretty much undeniably better off before. It's nothing but a tragedy - and their ill-treatment even continues to this day.
That's committing the same error the OP made, but in reverse. Instead of viewing your lifestyle as superior, you clearly view theirs as superior, since adopting the new one has been a net loss. "many of the stories involved are heartbreaking" - I don't doubt that. But all change comes with cost, though that one was certainly far higher than it should have been.
Citing past injustices in the pursuit of improving life doesn't mean the pursuit is incorrect. How about all the successes? Slavery was partially under the guise of improving lives (recently. Slavery has existed for far longer than we have records, usually the losing warring culture becoming slaves for the winning), but so was/is removing it.
In some ways, at some times, the effect is the same. What about the others? Should the pursuit be abandoned entirely?
The debate can be made more general: should we abandon everything that has ever caused suffering? Should only 100% successful lines be pursued? And, as no action is totally identical to a previous one: what's the measure used to tell if something is adequately different to be worth a shot?
edit to match edit: OK, so their problem is current ill-treatment. That is wrong. But that's still not the only thing that happens with cultural assimilation, nor does it always happen, nor must it continue indefinitely. If it improves at any point in the future, would it have been worthwhile? If 100 years of suffering result in 1000 of improvement, was it right or wrong? Not "could it have been better", is it right or wrong to suffer to gain improvement, or to impose suffering to grant improvement? We're debating broad decisions, not issues with a single choice. There's always something wrong with a single choice, and those nuggets of wrongness don't decide whether the core choice was right or wrong as a whole.
Good intentions almost always fail. People deserve respect. Superiority is often an illusion. Motivations are multifaceted.
I know I'd be happier with a simple life, and - perhaps romantically - I imagine that these people might have a better life than we do. Realistically, that's just as likely as the opposite - because, for all the interesting things our lives have to offer, there are some deep-routed problems we face, that we're very far from solving.
I think I said it in another post - but I'll reiterate before signing off .. I really hope this tribe is left alone. If a lot of contact is made, I'm sure no good will come from it.
EDIT: Nice debating with you btw.
Quite a few people choose simpler lives voluntarily. If they're happy, that's fantastic, they made the right choice. I de-clutter occasionally, which is a similar choice. But I see no reason that any style of life could be without deep-rooted problems. Ours is most likely ennui; I'll take that, because it's a personal problem that can be battled personally, and solved. Our culture could be better for such things, but not without other costs / problems which really can't be predicted, so I won't try. Many more "primitive" cultures have problems which are less solvable by individuals - food, safety, health, and yes I'm oversimplifying and it could be insulting, but it's more true of smaller, more isolated, less-technologically-advanced cultures than it is of the rest of the world.
We have far more individual options than they do, if only because we can choose to do without them (see: Amish). Which may be the root of the problems with our culture. But I like personal problems. I can fix them. I can't fix society as easily.
edit: I've enjoyed it too :)
Bullshit! While morals are about distinctions between right or wrong, the only moral debates worth having are ones that are about conflicting moral principles. In this case, between the moral principle that says we should allow people to determine and preserve their own culture and the principle that we want people to have the highest quality of life possible. It involves clashing interests and ill-defined concepts, so, yes, you can have it both ways. That's why it's a debate.
No, they're saying that they believe their beliefs and way of life are superior, therefore they have a moral obligation to improve the lives of those less fortunate than them.
Whether they're right or not is another issue, and as there's no objective way to measure such things, there is no actual correct view. If that's their belief, they're entirely justified in taking that course of action. Your belief is apparently the opposite, so you're entirely justified in preventing them from doing so. But what they said is not total bullshit, it's just opposed to you.