I'm indebted to Andrew Gelman's blog http://www.stat.columbia.edu/~gelman/blog/ for this lead:
John Huber and Piero Stanig accuse compassionate conservatives of "simple material greed" here http://www.iserp.columbia.edu/workshops/downloads/huberstanig.pdf:
We [Huber and Stanig] analyze how institutions that establish the level of separation of church and state should influence the political economy of redistribution. Our formal model describes how incentives for charitable giving, coupled with church-state institutions, create opportunities for the rich to form coalitions with the religious poor, at the expense of the secular poor. In our analysis, religion can limit redistribution — not because of the particular faith, belief or risk attitudes of religious individuals (as emphasized by others) — but rather because of simple material greed among the rich and the religious poor. We explore how church-state separation will mediate efforts by the rich to form electoral coalitions with the religious poor, as well as the implications for the size of government, charitable giving, and the welfare of various social groups.
So, what's level of proof that justifies "simple material greed" (an inflammatory term - why not the more neutral "self interest"?)
Huber and Stanig's paper has propositions and lemmas and equations, but I didn't see any actual data in there.
In other words, they are making an argument based on logic rather than empirics, much as Thomas Aquinas might have done in the 13th century when math was more primitive. To put in bluntly, there's a good chance this paper it itself a religious argument dressed up in equations.
As Bee wrote in a comment on Gelman's blog, "greed" seems to be used in an inflammatory context. The word occurs in the abstract, and once in the paper itself, on page 32 of 36. Even there it's qualified: "Instead such effects MIGHT be due simply to material greed" (emphasis added).
I'm not a conservative, and might or might not be compassionate, but this use of inflammatory language seems unfair.