At that point in the game you do have a choice: to do the unthinkable and survive or just to just be shot and die. I'm pretty sure the actual message is that to just die is the choice you wouldn't consider, just like quitting the game afterwards and uninstalling. It's kind of ridiculous, and I think that's the point.

That's kind of the point. Most other war games don't give you a choice either, but we find that acceptable because they reward us. Of course, this isn't how war actually is, but we tend not to criticize that despite how a lot of these games are blatant propaganda. Spec Ops turns that around and actually makes you face the consequences of your actions. It even points out the excuse of the lack of choice.

It’s essentially a reflection of how Walker feels in that situation. You’re pretty much supposed to feel like you didn’t have a choice because at the same time that’s how Walker felt.

Even though Walker did have a choice at the very beginning. He was supposed to scout the area out and return with his findings, he was never supposed to go deeper into Dubai like he did. But at every step he convinced himself that he had no choice but to do so. Culminating in the white phosphorus event.