Paris Jackson hates Bieber because he wouldn't speak up about teenage girls cutting themselves. Paris thinks Justin is a terrible role model for young girls.
She was enraged after some of Justin's female fans started tweeting about cutting themselves as an expression of love for the singer and he went radio silent, rather than talking the girls out of it.
Paris got very angry after seeing the pics TMZ posted of Justin smoking weed in a hotel room in early January. She thinks he owes his fans more as a role model. Paris also thinks Justin's various missteps in the hood are "a disgrace."