I've experienced the "Idiots attack" recently as well. And I don't think it's a n00b thing. n00bs don't drive well, but most of them listen when you explain them the meaning of blue flags, etc. Sometimes these idiots come few members of a team. Not deliberatly wrecking per-se, but do enough silly things to ruin a good race or many (as others noted, pitting out with zero respect for other drivers, getting in between the leaders with poor driving and unexpected behaviour, laughing after an accident, etc).
Maybe a Licencing system is required. Here's my suggestion:
1. Let LFS have a built in licencing system. This system can be a combination of offline hotlap times and tutorial (the LFS tutorial) times. Winning online races could add credit for these licenses. Maybe even different licenses per car. i.e. slow hotlap = novice licence, superfast = alien licence etc. Maybe even something along the lines of novice licence for at least one car on a category (SS, GTR, FWD, etc) grants you a novice licence for all the category (same goes for "better" licenses).
Now, the licenses don't do anything by themselves, HOWEVER, server admins can decide what kind of licenses they allow on their servers. So complete n00bs servers would not have any license limitation, normal friendly server will require novice license, and servers with superfast drivers will require alien license.
I know a licensing system has been suggested before, but as others said, it's getting kida annoying lately... It's sometimes really hard to find servers without idiots on track.