Vash's philosophy isn't so much that killing is wrong no matter what, it's more that he believes people can change and that as long as they are still alive they have an opportunity to realize their mistakes and make up for them. Basically Rem's saying that "the ticket to the future is always blank". It might have gotten a little warped into more general pacifism in the anime. >_>
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The only certain death in the universe is Mother Hitton's Littul Kittons.
Not changing this line until I beat Seven Heroes (2/24/07)