"Rhodesian arrogance"? Maybe just in response to the terrorist arrogance of shooting down civilian airliners?
Maybe Kenneth Kaunda was so disgusted with the shooting down of those airliners that he actually sympathised with the raid and therefore directed the grounding of the MiGs?
"A Mig 21 in the hands of a competent and committed pilot is a potent force". I wonder how 'potent' it is during taxy out and take-off? (Got to get through that phase first!)