I understand your reasoning, the outcome is the same, an innocent civilian dies.
Armies wage war, wars are visted upon civilians, the principle difference to my mind is the nature of the killing.
Bombing from afar is arbitrary, if you're in the circumference of the blast you're going to get hurt, the camps were completely different.
You would be selected to go to a camp on the basis of your offence, once in the camp, you were selected by means of ability and health, having under gone that selection you were again selected several times over to go on various lists, it's the picking out that makes it different.
Your analogy is a difficult one to counter, the people on the plane were prisoners and murdered by them, if it were an empty aircraft they may be allowed some sway, tough one to call.
It's a bit like our disgust at suicide bombers, it's just an effective way (for them) to deliver ordinance, or as I tend to say, go boom.
Personally if I'm going to be killed by someone I'd want them to die in the process, hopefully, as I'm going up, I'll pass him going down.