As far as the Sentinelese are concerned, war is not over. Every time someone visits them, the invasion begins anew.
Meanwhile, we do have the technology to contact them without giving them lethal diseases. It doesn't have to be like the Americas all over again. We can screen potential visitors for a wide range of pathogens, make them wear protective suits, vaccinate the local population, and treat them if they get ill nonetheless. The problem is that they want none of it, so any attempt to vaccinate or treat them will end up being forceful.
Meanwhile, we do have the technology to contact them without giving them lethal diseases. It doesn't have to be like the Americas all over again. We can screen potential visitors for a wide range of pathogens, make them wear protective suits, vaccinate the local population, and treat them if they get ill nonetheless. The problem is that they want none of it, so any attempt to vaccinate or treat them will end up being forceful.