I personally wouldn't because for me it's like taking away the persons chance to recieve God's truth in which they might other wise have gone on to love and worship the Lord. I want people to live on hopefully accept God's story of love and grace and in turn worship Him with their lives.
I don't have a problem with someone else doing it, I just don't think I could kill in self-defense.
Do not conform any longer to the pattern of this world, but be transformed by the renewing of your mind. Then you will be able to test and approve what God's will is—his good, pleasing and perfect will.
Rom 12: 2