I think that "chivalry" in a war may be a nice idea early on, which must get lost, when you face the truth.
It may be an idea of those far behind the lines, or those who only read about war in a book.
Once you get into the whole sh*t, these "finer sentiments" will quickly wear off (if you ever had them),
when you see comrades die. They were soldiers at war, and they shot at the opponent to kill him.
So why should they stop shooting, when his aircraft is only yet half damaged?
To save a crew's life, who have made an emergency landing, would be almost arrogant pride in the eyes
of the soldiers in the trenches; it would be playing god. Like "I decide, who deserves to live, or to die."
Still though, many people are not "natural soldiers". Udet first had to overcome the hesitation to attack
an enemy aircraft. And some may never have really tried to bring an enemy craft down.