What exactly is an “abolitionist church”?

My church First Presbyterian Church of Berkeley, CA has supported the work of the Not For Sale Campaign, a self-described "abolitionist" organization aimed at ending trafficking in human beings. (See for instance, a talk by David Batstone, the leader of Not For Sale at FPCB.) I'm generally supportive of the work of Not For Sale. One concern I do have with Not For Sale is its use of the word "abolitionist", especially as applied to churches. I have been hoping for a stronger definition of what an abolitionist church actually is from Not For Sale than what is currently there (at least as of the end of June.). The page describes "Action Steps" that a church might take to become part of a "movement of Abolitionist churches" but does not define the term "abolitionist".