Imagine waking up one day in a world, like ours, but with a parallel society alongside it that outnumbers it, say, ten to one. They dress in strange robes that seem shapeless and have unusual patterns on them you’ve never seen before; they talk of kukesh and sava instead of “right” and “wrong,” and the virtue of maor, and they try to translate these words into your language, but when you try to compare them to things you care about–love, family, individualism, freedom, happiness–they make a face and shake their heads.
“There’s no argument” doesn’t fly. There are obviously arguments. You may or may not find them compelling, you may or may not end up being swayed by them, but…they certainly don’t boil down to “I don’t care about these weak people.”
The most obvious of those arguments has to do with the “wanted contact” bit, and has already been expressed well by @morlock-holmes. The right of the conservative parents to live without being saddened by cultural erosion doesn’t trump the right of the children to information and freedom, in either a utilitarian or a deontic sense. And many people, in all cultures, have all sorts of good reasons to want to get out of their native cultural milieus.
Regarding language preservation etc., the argument is basically one of “who pays the cost of this upkeep?” Yes, it is cool that English has a phrase like “Christmas present” that is wonderful and resonant and doesn’t map well to anything in Laikom. Is it worth having a hundred thousand kids be locked out of the global job market, or having them be second-class citizens in the global forum of ideas, for the sake of preserving their access to the Christmas memeplex? Is it worth leaving them in a social ghetto where their choices of habitat, their choices of friends and life partners – and, yes, their reasonably-available choices of culture and subculture, because the overwhelmingly-dominant culture is always going to have the most internal diversity on that front – are severely restricted?
This is not a matter of sneering.