While people like to say they "stole" things, there's no evidence they ever took something that others actually cared about or took the least interest in protecting. The Elgin marbles were just flopped around a field and no locals seemed to care at all. Some of the items were purchased directly from their owner at a price negotiated with a willing seller.
I think the British museum is proof of how scholarship and gentle care can preserve our past and create something that people love to visit and learn about.