On the obverse, it's just as likely the American pilot returned to duty to continue his bombing runs until the end of the conflict, killing hundreds, if not thousands of Germans.
That's another excellent point to make. You may spare someone because you think of it as the right thing to do, but the live you save may cost you, and innocent people as well, even more later on.
On that note, I spared the Carthage in the game. Why? Because it was a s**tload of GTVA advanced tech and a semi-worthwhile space-frame that could be used for anything. Not to mention high ranking prisoners that could be interrogated and prove useful later. It was a decision purely about the acquisition & denial of resources to the enemy - "Saving lives" wasn't a thought. Those people put on the uniform, they made the choice, even if they were conscripts.
That was excactly my reasoning. I was in full-on cynical "no-mercy" mode at that point, but I was not out for revenge, and the Carthage seemed like a valuable asset. I guess another thought about the matter is: You can be without mercy, but also still trying to avoid
unecessary cruelty. There is a difference between killing helpless people in cold blood to achieve victory in a war, and killing them out of rage/revenge/sadism etc.
This leads to another thing, that is probably one of the biggest thoughts about behaviour in basically any situation: Do you do something because you feel like it out of intuition, anger, compassion, etc. Or maybe you do something because you want to achieve a clearly defined goal. Or maybe you do something because you have a certain set of principles that you apply to a situation, no matter how the consequences may be or how you feel about it.
This is why I spared the Carthage, ordered my wingmen to kill the fellow UEF pilots and so on.
Now this is especially interesting, because ordering someone to do your dirty work is something extremely common. The ones that do the deed can claim they were just following orders, and the ones giving orders don't actually have to do the deed themselves. So, in a way no one is truly absolved of their crime, but both parties feel better commiting it. Others may have thought different at that point, and would have thought something like: "If someone has to do it, I will do it myself, so no one else will get tangled up in this", thinking that killing them yourself is the more moral choice. (Only where not killing them at all is not a choice, of course)
Now, I think this derails the discussion a bit, towards more of a general "ethics in games" line of thought, but I also had a few more thoughts about moral behaviour in games.
Inside this game universe of course there is the problem, that if you want to advance in the game, you may have to do such things. There is no alternative that allows you to completely spare those virtual people and the story will have you hooked, so you really want to know what happens next. So in a way, to act "moral" you'd have to abandon your game, rejecting both the choice to kill or to order to kill someone, at the price of never being able to finish a great game.
That's bull**** in a way of course, in the end you can always say "oh, those aren't real people, just some 1s and 0s", and especially with a story as suspenseful as in BP, you probably won't be able to resist trying to know what will happen, and how it will happen. But if you were truly and completely disturbed by the thought of doing horrible things yourself - even inside a game - you'd actually have to do it.
I don't think anyone would do this in BP, but it is at least imagineable. It's like walking out on a movie in the theatre out of protest. But even there, you may only witness outrageously bad acts or horrible quality in directing or something, you may never have to pull a trigger yourself. Games do take it one step beyond in that respect. I think with other games, this has probably happened before, and not just angry parents returning the cool game their children want to play, but honestly people abandoning and/or returning a game they could not finish, because of something conflicting with their moral principles. It probably isn't a common thing, but I'd say it does happen from time to time.
