[He can't deny any of that, though mentioning more merciful killing stuck out more than the rest. If he was in one of his off moods he probably would give a small laugh at that, but he doesn't.

However, it did bring up something in mind after he sees where the shots land. Yes, they are vital enough to be deadly, but it might not always work. Immediately he knows Armin is a an insightful person and so he tries a different approach. The comment about mercy has him thinking, even though majority of the time he's never showed mercy, or at least not lately.]

Say the situation calls for not having to do any killing, but you still have to stop someone immediately. [or something.] Where are you going to shoot then? [Whatever was dealt with back home isn't the case here after-all so things can be unpredictable. All he did was point to the target urging to be shown rather than to be told where.]