I watched a program about the Spitfire the other night. Lots of interviews with veterans, some claims were made that Polish pilots would attack parachuting aircrew, I am not sure if these can be substantiated though.
The veterans interviewed about the battle of britain made it clear that they felt that they were attacking machines, not men. I believe that this would be an effective coping mechanism to allow them to mentally survive the experience.
I am lucky that I have never been in the situation where I have been forced to kill or be killed so I will not comment on the morals of it at all, except to say that it is difficult to get your bullets on target when the target is the size of an aircraft. Attacking a parachutist would seem to be an excersise in futility and it would not be a good idea to attack something that can do you no harm in an area with people whose main aim in life is to kill you.
Nice shots though
