One of the critiques of the Emergent Movement is "Because they're for everything, they don't stand for anything." Chapter 4 of The New Christians is about theology and specifically how theology should play a part in the world.
Jones attempts to argue Emergents believe theology is constantly changing. In other words, the failure to constantly filter theology through the context one finds himself in is harmful to he and the church as a whole. An example Jones gives is the Left Behind novels. How many people developed at least a part of their theology based upon what they read?
I know of people in churches that read the latest and greatest on the best seller list at the local Christian bookstore. Sadly, they're not sure how to filter what they read. Does it really add up to what Scripture teaches? And for that reason, their theology (as fragile as it is) is affected.
I'm with Jones in this chapter: "Good theology begets beautiful Christianity. Bad theology begets ugly Christianity."