I don't really mind the younger players, and have met alot of them that were very respectable players (like 'stealth', I was amazed to find out how young he was). They are the next generation of flight sim players and we should be welcoming them to our ranks, if it wasn't for the influx of new players, we would all go the way of Atari and become extinct.
My only complaint is, as some of the others have mentioned, the constant play by play on channel from some of them. "I'm going to shoot this guy", "I'm going to turn left", "he's shooting at me"... I think the response from alot of us is to call them squeakers and start bashing them for their age and that's not right especially when comming from an 'adult' who supposedly knows better.
Instead of calling them squeakers, I think it would probably be more productive to tell them specifically what our problem is with them, i.e. "We don't need to know everytime you pull your trigger." would be far more constructive than a "Shut up you stupid squeaker."
Bustr once made an excellent point about the anonimnity of the internet actually intensifying personality, if a person is a dk head in real life, he is doubly so on the internet, that said, I think alot of us sure as hell wouldn't be bashing someone else's kids in person so I'm not sure why it's acceptable to do it in game unless your just a jerk in real life. Give them a break, help them out, tell them to STFU if they talk too much, but don't lower yourself to bashing people because of their age, that's just a nasty way to be to anybody and only serves to lower the standards of the fight sim community.
Act your age in other words, and don't be surprised if the younger players do the same.

-Twitchy