My guess is this.
Many of these web sites are new. They came about during the anti Bush years and thus developed a following of individuals that were accustomed to finding fault in everything the acting administration did.
This worked out fine during the primaries and the general election as they still had the opposition to aim all their fire at. Well, that all came to an end when Democrats controlled the House, Senate and the White House. They needed something to keep their clicks going and their followers donating to their pet causes.
They didn't bother to find a new method of doing business as the old business model is the only thing these sites know so they turned their guns on their allies and opened fire. When I say allies I mean in the sense that they are much more likely to side with legislation being worked through Congress with the bunch in control now than if there was a Republican controlled Congress in session.
I'm not sure what it'll take to encourage them to turn their guns on the real opposition and not all of it on those that are no doubt pushing through legislation that at least addresses some of their concerns.