Japanese aerial exterminating action?

[GuerraCivil]

One of the controversial subjects of the air war during WW2 was the question about parachuted enemy pilots. Were they targets to be destroyed in every opportunity available or left in peace by a unwritten moral code between the pilots?

I became around this subject first time when reading memoirs of Galland, Marseille and some other European pilot celebrities. They condemned the killing of parachuting pilot considering it as a crime against the "unwritten laws" of war. However, after studying more the history of airwar, it became apparent to me that strafing attacks against parachuted enemy airmen were quite common.

The most systematic killers of parachuting pilots were without doubt the Japanese. Chinese, Soviet and Allied pilots reported that Japanese attacked the parachuted pilots systematically continuing to pursue them even on the ground, if parachuted pilots managed to get there. To save bullets, some Japanese pilots used their wingtip to cut off the cords of the parachute.

I must admit that reading about this practice it gave me quite repugnant picture of Japanese fighter pilots. It looked to me that cruelty and sadism were something that came from the cultural values regarding the warfare (like the treatment of the PoWs). As one Soviet pilot said: "it was simple Samurai cruelty".

However, to understand this darker side of the flying samurais, one should also study the combat principles of Japanese Army and Navy Air Forces. Japanese Army Air Force (and very probably Navy Air Force) had a principle called "aereal extermination policy". This meant that enemy airmen were enemy´s resource to be eliminated in every opportunity, specially if they were parachuting to safety over their own territory. In other words, pilots were ordered to kill parachuting enemies whenever possible.

So my question: are we talking of the "simple Samurai cruelty" or soldiers carrying out literally the orders given to them? What made Japanese pilots kill systematically parachuted Chinese, Soviet and Allied airmen in 1937-1945?