I can see your viewpoint (phrased a lot better than NJ's rant). I think we'll have to agree to disagree. I do not feel that having music playing softly in the background compromises safety. If one were to listen to music too loud and was "jammin" as you say, then it could be an issue.
I'm not sure what classifies as "jammin", but you can be rest assured that I will not be playing air guitar as I taxi up to the gate. In reality, I probably wouldn't be listening to music during anytime other than cruise flight.
As far as the public's perception of pilots, they would never see me listening to music. In my opinion, I see far worse perception issues around the terminal. Some pilots look like an unmade bed...I know you've seen them. Some go walking around the terminal with a guitar slung around their back. Very few (myself included at times) wear their uniform hats. And as unfair as it may seem, some of us are very unhealthy...in all aspects.
My point (now that I've turned my own post into a professionalism debate) is that it does not affect safety OR public opinion. Our company allows, per the FOM, reading of company related material during flight. Why is it OK for me to read the latest company newsletter, but not the USA TODAY? Honestly ask yourself, would your cruise segment flying ability or decision making be degraded with music in the background?