it's considered not just self-defense, but actually brave and an act of compassion to kill family members and friends who have become zombies. Not being able to kill them is a sign of being too sentimental.
Why is it compassionate to kill a zombie?
Because they look different?
Because they can't think very well?
Because they're chasing and eating people, something their old self wouldn't have wanted to do?
Because they're presumably constantly hungry, which wouldn't be a pleasant experience, I guess?
I mean, I think it's fine to kill someone who is trying to eat you, but I'm curious about the compassion angle, the idea that If You Really Love Someone, you won't let them live as a zombie.