The flight sim community isn't very large but it is very dedicated. Enthusiasts of the genre are a unique bird; they're gamers by definition but probably the most "non-gamer" gamer, generally speaking, you're ever likely to run into. If you asked most of them, they'd probably scoff at any suggestion that what they're doing is playing games. They're engaging in virtual flight.
Which is why this attack is so despicable. A small, unassuming community of specialist enthusiasts has been victimized by someone, probably, as pointed out by others, a script-kiddie idiot who went after a target he knew would be easy pickings. Yes, Avsim should've had a better backup system in place. That doesn't change the fact that this was a pointless and malicious attack by a true blue jerk. I sincerely hope they track down whoever did this and prosecute him to the fullest extent possible.
(Admittedly, as a former flight sim fan myself, I may take this a little more seriously than most.)