As an avid Xbox Liver with a 10 year old brother who plays with me frequently (on Halo 4), I can say that not all children are the same. A lot of people bash him right away when he starts talking because he sounds young, even if he hasn't said anything bad at all. Half the time we'll just be speaking with each other and anyone with a mic will start calling him out.
I know there are some annoying kids out there, but assuming that because they're a kid they must suck and deserve to be cursed out is counter-productive and rude.
Also, I know adult gamers who whine more than kids, and just because your balls dropped and you have a deep manly voice doesn't make it excusable. Just saying.