I have yet to read the full report, but their statistics-based content analysis would seem to bear out my general impressions. U.S. news media tend to treat religion as a conservative force, but this means leaving out the voices of maybe two-thirds of religious believers.

I think this is due to the extremely vocal minority which is zealously religious. Most Americans have faith of one sort or another but are quiet about it and keep to themselves.

While more radical/fundimental groups are much more vocal and over bearing thus warrenting more media attention. From what I have seen those groups tend to cluster in the traditionally conservative base.