The civilized world has a spectrum of options other than invasion to deal with human rights issues. Normal practice is sanctions or trade embargoes, putting pressure on leadership to enforce a movement away from those practices. (And we both know that when the US invades Syria, Iraq, etc., it's not because their leaders are killing their own people... that's just part of the PR campaign to justify military action.)
I wouldn't punish the North Sentinelese for protecting their island, or for any of their internal practices. But they don't know any better, and my questions are more about whether we have any moral responsibility to help them get there, or if we just let them do their thing no matter what it is.