TommyGunn,
The problem with Hawkmoon's post is the false dichotomy between religious and political issues. For example, taxation is certainly a political issue, but if (as many claim) the American income tax somehow oppresses the poor, then Francis would not be out of bounds to say something about it. When it comes to government policies that really do oppress the poor, e.g. the minimum wage, he would not be out of bounds to suggest its repeal.
Conceivably, there could be a religion that contains no moral precepts about how we're to treat our fellow humans on this earthly plane (Buddhism, perhaps?). And for such a religious leader, just saving souls may be enough. Catholicism is not such a religion, however.