You're overthinking this with hypothetical nephews. In reality, ladder guy is just being a sociopathic asshole watching a kid burn while clutching his property rights.

The "calculation problem" doesn't apply when there's literally a child screaming in a burning building. You save the kid, deal with consequences later. Anyone who'd let a child die over ladder ownership has broken something far more fundamental than the NAP.

Pure NAP absolutism is moral autism.