This is a real nest of worms! Basically I tend to agree with such artifacts being returned to the original owners when of such cultural or religious/spiritual significance. I am of the firm opinion, for example, that the Elgin Marbles should go back to Greece.
I did read however, where a government destroyed a collection of precious artifacts, held in a museum, but were significant to a religion other than the "state" religion. Obviously these artifacts would have been safer elsewhere?

I'm not really any further forward - still confused.

Eddie