@Frostisss
The whole thing was to make it clear that this world has a different mentality than our own, where kidnapping and the like is not nearly as uncommon as it is today.
It shows the MC´ does still value life but is prepared to do what needs to be done, its a similar mentality to what you would have in the military.
The imagery of the flashbacks with the bear could also suggest that the MC, considers the people he is shooting at to be" beasts ".
Or that he doesn't mind taking a life if it is to save another. ( Its also how he died just a few days ago )
It is however pretty clear that he still has some issues with killing people afterwards, which shows he isn't completely disincentivized to it, unlike some other main characters.
Shooting somebody who uses a little girl as a meatshield while trying to kill you would not get you in trouble even in our world, I don´t see what the issue is here?
Killing in the defense of another is often legally justified as well.
They were, most likely at least, kidnappers... but you also have to consider that they started shooting at them as soon as they noticed the boat was there.
Granted it was with bow and arrows and they were failing miserably, but that really doesn't matter in the grand scheme of things as they had a crying child in chains used as a meatshield.
Any reasonable person would assume they were in the wrong here, and I don´t find it strange that a person who is told not to use guns for violence would shoot to kill if the situation required it.