Maybe. Seems like it is making it worse though.
Maybe it takes a certain maturity to be able to learn mussar, and otherwise you just remain a jerk and also are misgaeh as a “baal mussar.”.
Joker seems to be about 9 or 10 years old. Way too young for mussar in my opinion. Although, you have said you know who he is, so if he is older, maybe he is just very immature for his age. But that isn’t really his fault either-maybe his father’s.