I'm not very sympathetic with OP's positions, but I do think these analogies to individual theft are pretty weak. Who owns shared cultural artifacts? The government? The Ottoman government was in charge of Greece when they gave the Parthenon marbles to Lord Elgin. Was that stealing? If so, does the current Greek government have the authority to do what they want with them? And what's the difference? Both governments have supporters and detractors within Greece. There isn't nearly as clear of a distinction as most people want to think.