I've had a motorcycle license for 40 years and am an earned Life Member of the AMA.
Loud Harleys, in particular, give me a headache.
Our church in on the main city square in Morristown (NJ) and we can always hear these things driving by during a service.
Of all the good will I have personally tried to do regarding motorcycles, a loud Harley can undo it in a moments notice.
I cannot think of any non-motorcylist that likes the sound and I know plenty of long-time bikers (like me) who dislike it as well.
Overall the sound of these things has been one of the worst ambassadors for the motorcycle community (along with loud, illegal dirt bikes).
The original design of the Harely vee-twin allowed "packaging" the engine in a narrow space. But the single crank design required that exhaust scavanging would not be affective, thus power and efficiency would always be limited.
Without scavanging, the only way to increase power is to unmuffle. In fact they'd make even more power if the exhaust pipe were removed all together and the engine breathed directly from the exhaust ports.
There are far better, more efficient layouts available, but owners seem to prefer the "styling" of the vee twin. Thus the company builds engine based on style rather than mechanical efficiency.
The sound of a properly muffled Harley is not objectionable. Similar to a large lawn mower or other agricultural equipment.