when someone declare that you are mean, he/she means that you are not nice or you did disappoint her/him at the point or action been made from you.Hope you are clear now.
It means their too passive-aggressive to speak for themselves. Perhaps they were raised not to be "selfish" and this is their way to get around that. "I say 'we' because I'm speaking for the group-...
You could say, "Grow up," or "And insulting me makes you feel special, how?" or you could just roll your eyes, give him (or her) a disgusted look and walk away. Myself I usually say "Did you intend...