The last remaining isolated tribes should definitely be left alone. There is absolutely no reason they need to contacted by the modern world. Must we really destroy one of the last pure things that is left on the planet. Let them be and maybe we can study them from afar.
No one should be forced to interact with others if they have chosen not to do so. As long as they are not harming anyone by remaining isolated, it is their prerogative to continue to isolate themselves from others. They should not be forced to be in contact with anyone.
So few cultures still remain unmolested from the advance of modern society that the known isolated tribes of Brazil deserve to have their heritage protected. While there is surely educational value in learning the practices of these unique groups, their privacy, culture, and way of life is critically endangered and deserves to be left alone. I agree with Brazil's position that we should not force contact with the groups for whatever perceived gains our own society might yield from such an activity.
Isolated tribes in South America should be allowed to continue living undisturbed for two reasons. First, having not been exposed to the rest of the world, their immune systems may not be able to handle the exposure to various new pathogens, viruses and bacteria. Second, these tribes have consciously chosen to remain isolated, and their choice should be respected.
Allow me to make it clear that I do NOT support contentious interference with the tribes. Yet, there is valid reasoning behind my decision to say no. Given enough time, sufficient differences between the "modern world" and the isolated tribes will develop, creating new and unnecessary issues. Biological, physical and cultural differences such as immunity, dietary variations, morality, and culture will inevitable lead to potential discrimination against either or due to a lack of exposure. Though it is their right to remain alone, I have reason to believe that it is in the best interest of everyone to at least have contact with said tribes, as total isolation will consequently lead to more prominent issues.