If it'd been up to the Turks they'd have crushed them for use as road ballast.
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The Turks have already destroyed vast amounts of ancient Pre Muslim artifacts/temples/churches/etc.
The esteem the Greeks held the Parthenon and its significance to the Hellenic psyche and culture can be seen from the fact that at one stage during the War of Independence against the Turks the Greeks supplied the Turks with ammunition to stop the Turks destroying the Parthenon to obtain the metal supports contained in the temple!
The main point about the Parthenon Marbles is that they represent the cultural patrimony of the descendants of the ancient Greeks who are firmly in control of their nation...the Greeks. Of course the acrimonious debate has softened recently with major objections having been solved.
Bottom line: The frieze was bought illegally and should now be returned. London has made millions off it. Elgin cared more for his own acquisiton than he cared for the Greeks themselves and their struggle for independence.
Still, most of the stories about the Turkish governments and ancient monuments are poppycock. Private individuals, however, are a different matter.
You have a valid point, but the the frieze is better off in London because they will do a better job of preserving it.