Halfbaked boy.
Ok, then lets assume that the pilot is flying a type that is rated for aerobatics, only an idiot will go and try and teach themselves aerobatics, whilst in the UK in theory anyone can try, most decide that they want to learn properly to avoid endangering themselves and/or the aircraft.
You will remember from your basic training hassell checks?
H- Height Sufficient to recover by
3000ft (900M) AGL
A-Airframe Flaps and landing gear UP
S-Security Hatches closed and locked,
Harnesses secure, no loose articles
E-Engine Ts and Ps, fuel, carb heat, throttle and pitch as required
L-Location Clear of controlled airspace cloud and built-up areas
L-Lookout Clearing turns
So looking at the check list we look at the "S-Security" check, NO LOOSE ARTICLES. Why is that? Why bother?
If you had been instructed to do any aerobatics you would have had it drilled into you that even involved checking that you had nothing in your pockets that could come loose during aerobatics, anything loose has the potential to jam controls or cause injury.
We have all been flying when an unexpected pocket of air caused the aircraft to drop, why is that not going to happen when someone is unstrapped and trying to climb from one seat to another in a PA28, which of course is a lot tighter on space than a 747.
With respect to aerobatics a lot of people enjoy aerobatics and go out to learn how to improve their raw flying skills by learning how to do aerobatics properly. The same as some people enjoy touring or flying a taildragger.
In my opinion self taught aerobatics is likely to result in death....
Back onto the thread its all about recognising the risk and managing it to a sensible level. In this case its about a commercially rated instructor placing students at risk, a risk that they may have been totally ignorant to and one they assumed was normal practice, why bother??