I actually sympathize with the "loud pipes" theory to a degree.
The problem with that is what we bikers consider "music" is of course perceived by the non-riding community as an in-your-face annoyance, and is mostly viewed as another obtrusive noise, much like an airliner flying directly overhead or a jackhammer working outside one's bedroom window.
Thus the positives of the pipes (e.g., great sound, to us) are more than cancelled out by the "damage" they do to our image as bikers.
Latest case in point: I guess some of you have already heard that the city of Denver, Colorado has just outlawed all other motorcycle pipes for street use--except stock. They have deliberately targeted motorcycles with this ordinance.
Naturally, the AMA is trying to lobby this new law back out of existence.
For more details, hop over to the AMA homepage. You should see the link to this announcement there somewhere.
Unless we as bikers show more consideration for what we're doing to the non-riding public (e.g., riding by sounding like a WWII bomber), I'm afraid we'll see a lot more cities pass laws like this one in Denver......
All of the above is (in part) why I made the earlier pitch about "loud colors