Blow-hard Christopher Hitchens (who I agree with on this account) rightly calls for the frieze pieces to be returned to Greece, especially now that they have an excellent facility to house them. (For a long time, the claim was that the marbles were better cared for in England - an imperialist argument if I ever heard one!).
I think it's great that the Acropolis museum is re-opening the conversation about the return of the pieces to their home. These are hard decisions and if it did happen, a great reshuffling might occur in museums all over the world, but I think people have only to look at the relative success of the policy on the return of Nazi looted art. While a museum or individual's return (no refunds/no exchanges) of a piece might be a momentary financial hardship - what it earns the individual or organization is a lot of respect for doing the right thing.
O my country, O unhappy land,
I weep for thee now left behind;
now dost thou behold thy piteous end;
and thee, my house, I weep, wherein I suffered travail.
O my children! reft of her city as your mother is, she now is losing you.
Oh, what mourning and what sorrow! oh, what endless streams of tears in our houses!
The dead alone forget their griefs and never shed a tear.
The Trojan Women
Euripides
415 B.C.E