I am organising someone to oversee driver etiquette(clerk of the course) at MTC 2014 so these incidents will be avoided. They will be in the control tower watching everything that happens. People will be spoken to for dangerous behavior. If they persist, they will be asked to leave.
If people do practice on simulators, they must drive as if they are in their car they maintain and pay for it running costs. At least they will then instill 'habits' of not performing GT5 maneuvers.
You really have to have these in your list of mental prep before entering the circuit with others:

• Understand your car.Tyres, brakes, handling.
• Be aware and honest of your skill level. Get lessons/time with a driving instructor.
• Understand the nature of the track.
• Awareness of the condition of the track.
• Take time to get the car up to its operating range before you push.
• Be courteous while driving whether you are being passed or passing people.
• If the organiser says 'no passing in corners', respect the rules(*at MTC only circuit class cars can pass in corners. It is in the reg's)

There are more, but that should help reduce chances of accidents.