I’m not sure how someone who wants to outlaw abortion defends capital punishment, especially if they also believe in the possibility of redemption and forgiveness.

But in the case of war, the answer is self-defense. Killing in war may be justified to defend others’ lives and freedom. That doesn’t mean all killing in war is justified — far from it — only that it’s possible to distinguish one person killing another from a nation engaging in warfare.

For example, under Just War theory, the nation must have legitimate cause (such as self-defense), decide to go to war under legitimate authority (such as a democratically elected government), and act in a manner proportional to the task. Many wars do not meet this standard, but it’s possible to defend, say, Britain going to war against Nazi Germany as legitimate in a way other killing is not.