They are far from prudent and probably couldn't care less about whether they "embarrass themselves" or not. The liberals at CNN apparently enjoy flaunting their bias. I'm sure they don't see it as a "lack of professionalism", but as a bold statement (like the X over our VP). I'll bet the only ones talking about it will be preaching to the choir, anyway. (talk-radio and conservative websites).
CNN - They really are the Clinton News Network.
That being said, I felt the "questions" were answered very well despite the actual intention of CNN. (Yes, I know - I'm preaching to the choir.)