Capt Wally, I am quite aware of radius of turn and manoueverability of large and small aircraft.
Firstly radius of turn depends upon one thing and one thing only and that is airspeed, not size of the aircraft. Due to the incredible hi lift devices used on many heavy aircraft, they are able to manouever at speeds similar to some lighter aircraft, they will therefore have a similar radius of turn. An A380 at mlw has an approach speed of 137kt, a Piper Aerostar could easily be doing 200 kts in the circuit. At these speeds the A380 will have a significantly smaller radius of turn.
Secondly, manoueverability is dependant upon two things, size of flight controls and thrust available maintain airspeed. Many larger aircraft have stabilisers, essentially meaning that the entire horizontal tail surface is a flight control. In roll they not only have relatively large ailerons which are augmented by spoilers. This means that if required the aircraft has incredible manoueverability in pitch and roll. Additionally if abrupt pitch changes are made, the aircraft most likely has sufficient thrust to ensure that the aircraft can climb away easily. Compare how a lightweight twin jet such as a 737 is able to climb away compared to a Cherokee 6 or similar. You cannot tell me that the lighter aircraft has a better ability to climb out of the way of trouble.
There are many factors that effect the amount of airspace an aircraft may use when manouevering, but weight is not primarily one of them. The primary factors are speed, thrust and flight control capability.
I am not condoning any unprofessional behaviour when flying in CTAF's etc, just trying to point out the flaw in your argument regarding weight and manoueverability.