That fact that you are that upset over being called a kid only points to you being immature. Making the kid insult all the more apt.
Rule #1 of Online Gaming, don’t let anything anyone says get to you, just remember its a game.
Seriously, if someone insults you just block them and move on with your life, if it really bothers you that much let your close friends know to block them too.
The last thing you need to be doing is jumping onto an online forum to complain that someone hurt your feelings.
Naming is wrong because it can easily be abused by people to harm or hurt anyone without reason or fault.