Wallis reminds us that Jesus wasn't "pro-rich," and extrapolates from that that Christians must support higher taxes. Now, the New Testament obviously enjoins us to care for the poor. But what mix of policies is best suited to do that is a practical question. Conservatives happen to think everyone is best served by a low-tax, high-growth economy and by social policies - e.g., welfare reform - that encourage the inner-city poor to work and marry.
To pretend that this mix of policies is forbidden by Christ is a frank abuse of religion. We can draw from the New Testament broad principles - value human life, care for the poor, create a free and just society - but we don't receive guidance about how to handle capital business expenses in the tax code or whether Medicare reimbursement rates are too high or too low. Jesus didn't work at the Brookings Institution.
At a practical political level, the Democrats have a problem, given that secular voters and the only- mildly religious overwhelmingly belong to their party. If they take Wallis' advice, say, to complain about the abuses at Abu Ghraib in the context of Genesis 1:27 ("So God created man in his own image"), many of these more-secular voters will respond: "What does opposing torture have to do with a book about God allegedly creating the world in six days? Are you nuts?"
Besides, teasing strict rules for public policy from the Good Book bears at least a little resemblance to the rules-bound errors of the Pharisees and Sadducees. And we know how much Chairman Dean abhors them.