In ancient Israel, the categories clean and unclean maintained identity and established boundaries, and contact with outcasts, sinners, or lepers made one unclean. In conjunction with the holiness laws and food laws, the priest declared who was in and who was out. The sinners, the outcasts, the oppressed, the poor, and the hungry were despised and were definitely out.
Gibbs and Bolgar, Emerging Churches, p. 118
Ok, let's see...
Where did they get any of that???
I mean, really, where in the Law does God tell the people that being oppressed, or poor, or hungry made a person or a people 'unclean' and "definitely out"?
While I don't have a list of the thing that the law declared unclean or said made a person unclean for a time, I have no recall of something like social status being one of those things.
In fact, one can find places in the law where room is left for the caring of those kinds of people. For the hungry, there were the rules about gleaning the fields, which can seen illustrated in the book of Ruth. It wasn't a welfare or handout system, they still needed to do the work of gathering from the fields, but it is there. And there are places in the law where they are warned to not show favoritism to either the rich or the poor, but to judge justly. There were laws about, for example, not keeping a person's coat overnight, so that they could be warm.
If they want to comment on how the law may have been twisted, they may have a point. But to me I do not think they make that distinction. At least in the above, they make it seem almost arbitrary, that the priests made the decisions based solely on their own opinions, and not on the Law God gave the people.