Mashable just posted this video where they got an employee by the name of Jon to listen to only death metal for eight hours straight. He did not like it at all. This was juxtaposed with somebody else being forced to listen to classical music for eight hours straight and they noted the reactions.
Sure, for somebody not exposed to heavier music, listening to death metal is a jarring experience. Not to sound defensive, but it's dense music, so you need to train your ear to understand what to listen to. Some people just don't get it.