I may be wrong, but I see Scott's point to be that the predominance of Christians does not, standing alone, decrease crime or, more broadly, eliminate social problems that we see in our society. Again, I might be wrong, but it seems to me that one conclusion one might draw from Scott's study is that we won't see wide-spread reductions in crime or whatever based on broader willingness to self-identify as a Christian. Part of that, it seems, doesn't account for the idiosyncracies of individual behavior and the hypocrisy of some who claim to be Christian but act contrarily.
But if the point of one argument is that society is better served if its people are religious, and more specifically, Christian, then Scott's data would certainly seem to present a counterpoint to the idea of any such correlation.