On the absolute surface level, you make what seems to be a good point. I don’t think that point holds up to scrutiny, though, and such lazy (no offense meant by this; I’m not calling you lazy, only the point you’ve made) reasoning is not far removed from using “think of the chldren!” to justify an agenda.

Any dwelling that is not yours is generally assumed to be off-limits absent an invitation to enter. Ignoring that and breaking into said dwelling is implicitly a statement that you are disregarding the safety and security of the inhabitants. That further implies that you equally have no regard for the health and well-being of the inhabitants, as your actions are putting your needs or desires ahead of theirs. You have, wittingly or not, made yourself a threat to the inhabitants of the dwelling.

Responding to an immediate, credible threat against one’s life with lethal force is quite rational.

I have no doubt that this will have detrimental long-term effects on the boy. I also have no doubt that the very experience of being present during a home invasion would have had similar long-term effects.