Except most of the places that they took artefacts from are not warzones, or under threat of war. Egypy, Greece, Nigeria, Turkey, the US, India, China, South Africa etc etc all have the capabilities to take back and house their treasures safely. It is purely British arrogance to think that many other countries don't treasure these objects nor able to look after them.

I think preservation vs plunder argument is an easy copout for those that are keeping stolen goods.