Agree with everything said.
My real point was to crystalize it in our minds and think what to do if this situation started to emerge. So what would flight deck crew / controllers course of action be? The intruder would obviously be seen on ground radar and then on TCAS. I remember reading an article about Spitfire v 109 where they said it wa almost a set format. If you were in a Spit and got bounced then you went straight into a tight turn which the 109 was unable to replicate to the same degree. If you were in a 109 then you pushed the stick and dived away taking advantage of the negative g fuel system that the Spit didn't have. I'm guessing therefore that if I was approached by an "intruder" then I'd just adopt a maximum rate climb in the hope that they couldn't follow. Obviously some help from a controller would be needed as to what was a legit contact and what was unauthorised, info that until the later stages (i.e. it became obvious) TCAS couldn't give.
Its getting heard all the time but I agree that to change or way of life or our freedom to live means that these mad men have won a victory. It was never my intention to suggest banning GA or to make flight plans mandatory for all GA trips, as in say Colombia (but for different reasons)..