The North Sentinel people are not actually fully isolated. They had contact with colonial authorities in the past (the British went on the island and even kidnapped some of the locals they found, an elderly couple and 4 kids. The couple died not soon after and the kids were sent back) and there was some peaceful contact with Indian anthropologists up until 1997. The 2004 earthquake and tsunami affected the island pretty badly and disturbed their fishing grounds but aerial survey of the island confirmed they survived and adapted to their new conditions. Most contact after that has been met with aggression most theories I heard about why assume it's because of contact people fishing illegally in the area or an epidemic on the island after one such contact.
The Indian government considers it illegal to contact them and will punish anyone who does it. That one American preacher that landed on the a while back was eventually killed by the locals and his death was ruled a murder but the Indian government didn't push for anyone to be prosecuted. The US government also didn't push for prosecution. So yea the Indian government wants them to be left alone.
My personal take on this is that if the North Sentinel Islanders wanted to be in contact with the rest of the world they could. They are not very far from other Andaman islands and they could build a raft or a canoe that could reach them. The fact they haven't done so means they don't wish to be in contact with other people. It's their choice to be isolated and it should be respected.
Funny how God punishes little girls in Texas for the sins of gay people in California.