click on your クラブ on your profile... then you'll have the 一覧 of クラブ you're in, then あなた click unsubscribe and its done ^^ But hey... u dont have to insult JB on the JB spot, ファン will obviously hate あなた a lot ;)
On your profile, go to your clubs. Locate the Justin Bieber club, and there should be a word 次 to it that says "unsubscribe". Click that and it should remove you. Hope it helps!!