Should the Parthenon Marbles be returned to Greece?

I'm all for it, it is not just "classy" as Stephen Fry said recently in a TV debate but actually it was since the very beginning an act of imperialist looting that would be frowned upon also today (and was already back in the day considered quite questionable). 

By all accounts, the marbles were looted by the British ambassador in Constantinople Thomas Bruce (alias "Lord Elgin") without any sort of authorization by even the imperial authorities of the Ottoman Empire, then occupying power of Greece. 

The marbles, which date from Classical Greece, exposed since the early 19th century in the British Museum, suffered from the brutal pollution of London in much of all this time and have been damaged by primitive restorers.

Meanwhile the Parthenon in Greece stands as a naked ruin, largely deprived from its original fullness.

Archaeological looting alert in Ptolemais, Libya

The Hellenistic city of Ptolemais (also known as Ptolemaida, Tolmeta and Tolmeitha) is being looted in an extensive and well organized manner. According to Ojos para la Paz[es] (Eyes for Peace):

Witnesses have declared that right now the coasts are being used for illegal trafficking. Also foreign bulldozers are visible, as well as digs and ships that look like fishing ships. Asking the locals what is going on, they say that there is people digging and do not want to be bothered. They are unknown people. In the excavated places men carrying vases to the ships can be seen. It is obvious that they are looting this site. We know that right now Libyan archaeological remains are being sold in Egypt and other countries.