Lending to rich Europeans would be a hard political sell at home. The arcane economics of foreign exchange earnings mean that the Chinese government cannot actually use its $3 trillion of foreign exchange reserves to build hospitals, schools, or a decent social security system at home. But try explaining that to the ordinary Chinese citizen who is wondering why his government should spend money (that he helped earn through the sweat of his brow) to bail out spendthrift Greeks who on average earn 10 times more than he does…