For drone pilots, it's rumored they actually have a lot of PTSD. You may be looking at a screen and ignore the situation now, but for healthy humans, killing someone will ALWAYS come back to haunt you, even if it's entirely justified like in self defense.
I think that is pretty speculative. I think a large portion on the population would not be haunted by killing others in a wide range of justified situations, particularly when it comes to defending themselves or family from a credible threat.
