Well, for starters, there's "Biebus" (since his fans think he's like Jesus). Chances hare, haters call him "Beelzebieber" (since the haters think he's like Satan).
"Beliebers" like having Bieber Fever, while haters dislike having the Biebonic Plague.
People who are into Pokémon seem to call him "Justin Bibarel".
And then there's "Justine Bieber" for the haters who purposely call him a girl.
The seemingly ubiquitous Grandpa nickname: "Jason Booby"