I think the challenge here is the fact that nobody — on either side — even existed when these things happened. Why is anyone beholden to some arbitrary point in history? How do we even determine that? Rome used to lay claim to the entire Mediterranean. Should that be restored to them because, well, history? So China believes that these people, their culture, their way of life, etc., is theirs because of a history that predates anyone being alive? For better or worse, this is Hong Kong now. The idea that they should have less say in what happens with their country because of some arbitrary point in history seems fairly archaic.
When we look at a people wanting to preserve their way of life — the only thing they’ve known — and weigh that against “well these people think it’s theirs,” I know which side of that argument is more rational.