I'm a member of myg37. Good forum. I will admit some of the cars are way too over the top. But people with BMWs do that too. Not about the car you drive, but how you drive (and what mods you do, I guess).
People with all cars can be jerks. I've had camrys and corollas try and take off. I usually just let them pass and have their fun.
Can't speak about all G drivers... but most should have common sense enough to know what an AMG/M car is compared to the base models. The G37 is a fast car, but nobody should think stock/stock it can compete with the M3/AMG/S lines... or even the 335i/is for that matter.
I was driving along side an E63 AMG last night actually. Had a bit of fun. But when she really pushed it, I obviously couldn't keep up. I hung with her though, handling on the 335is coupe is really amazing, especially in Sport, with the DCT traction.