It looks to me like because of his stature and face, and due to he fact that he's been treated like shit his whole life (I'm 100% certain), he feels the need to lash out on someone who he feels he musicianmogs (since it seems to be the only thing he can mog most people at). And it's not because he's annoyed that the trumpet player is playing, it's because society has lashed out on him because they mog him hard.
