I mostly agree with your analysis. It is very rare to see a real conservative on any of these shows. When they're there, they're mostly "balanced" by an opposing viewpoint, and usually outnumbered in their "balance". I'm not quite as pessimistic about the outcome of this kind of agenda driven show, however. Most times, when liberals simply speak, and particularly, as last week on MTP, when they're supported and encouraged by the host, they make fools of themselves. The vast bulk of America sees them for what they are and are not persuaded.
Letting them talk, even unopposed, often is the best way to make our point.