I would qualify that by pointing out that "loud pipes save lives". The guys who rev in parking lots are jerks but the guys who roar on the highway are better known as "still alive".
It's only valid in the context of being on a freeway and in no way justifies the loudness of the pipes.
The simple fact is that some Harleys are loud enough to make pedestrians ears ring....which as far as I'm concerned is the same as walking up and boxing a stranger on the ear - only without the actual physical contact.