This is what Dowding and Churchill apparently said on the subject:
"After dinner, they discussed the topic about the morality of shooting parachuting Luftwaffe pilots. Dowding suggested that German pilots were perfectly entitled to shoot RAF pilots parachuting over Britain as they were still potential combatants (i.e., going back to a new aircraft to conduct another military mission), while RAF pilots should refrain from firing at German pilots as they were out of combat and would eventually become prisoners of war once they landed on British soil."
Full text of the above quoted Wiki article here:
https://en.wikipedia.org/wiki/Attacks_on_parachutists