The only bad habit is teaching them exactly how to fight. Things like gunnery, ettiquette, backing off the throttle, using the tools within the game (dot commands, strat system, communication, E6B, plane strengths and weaknesses)... that's what I see lacking in the MA's newer players.
I'd wager 9 out of 10 guys are already itching to find a bad guy and pull the trigger. I remember when I first started in AH (barely)... I already knew deflection shooting, understood gunnery even though I wasn't anywhere near proficient, had a rough idea of which planes would turn, and which went fast... I just didn't know how to make all of them do those things on cue. I, and maybe I'm the oddball here, didn't need or want anyone to teach me things like BnZ, energy conservation, split esses, etc. I just needed some inkling as to how to fly. I knew once I could get and stay airborne, I'd start figuring the rest out. For me at least, gradually learning, making steady, albeit slow, progress over the years was what kept me interested. Since I started playing cartoon airplane games (Aces Over Europe, then Jane's WW2 Fighters, then the big online world of AW3ish, to AH1, to present) I have maybe 2 hours of formal training, yet I've had fun almost the entire time. There's something to be said for not being fixated on goals in a game, IMO.
Not to venture off topic too much, but I'm more concerned with having an arena full of guys who won't engage without an enormous advantage, and guys who just grab buffs and level everything from 1000' because they couldn't sort out the basics, than having an arena full of hapless noobs who just shoot wildly and auger when ever frightened. At least those hapless noobs are having fun.
Anyway, I think I'll have a beer.