LOL people used to say the same thing to me playing Desert Combat. All i did was jets so got pretty good in them. I could basically ground the other time for the whole game.
People used to say "your not helping your team, why don't you go cap a flag". They never realized that while i had them grounded they couldn't get close to my base without driving a ground vehicle. Made it pretty easy to win the game for my team.
Moral of the story if your beatin the hell outta the other team you are helping your team

Not really. If you're camping the sniper spawn (which I suspect he did) at the base you start at (not sure which base that is) killing those unlucky noobs who spawn outside the base (and yes most of them are noobs, it's BTB), you're not helping your team as much as you could be. You could be supporting the bomb guy or clearing the way inside the base so he can make his way through. The people that die, respawn, and have to run back to the other base will take care of the people outside the base.