They really didn’t strike me as liberal as much as libertarian. They constantly pierced liberal pieties with relish, and mustard.
I heard them say things that seemed liberal to me, but...I listened to them in the day before I simply stopped listening to nearly everything from PBS in general, and WBUR in particular.
That said, I liked the guys. I really did. And you are right, they did have a wide range of things they would skewer...:)