No, it's wrong because the NAP says so. If you want more information on why the NAP says so, there is plenty of data, even in other threads on this board, that I do not feel the need to rehash. If you or AyeYo will give me a definition as to why you feel murder is wrong, even though you disagree with the NAP, I will couch my explanation in terms that you will accept based on that framework.
And Yes, to some extent, you are asked to predict the future in every aspect of life. Every action you take is a risk. Even inaction is a risk, because of unpredictable factors of nature. That said, If you got on a raft with a knife juggler, you knew what you were getting into.
Yes, and the NAP is defined by "you". If I write a No-Non-Necessary-Agression-Principle that says that the NAP is wrong in certain circumstances, does that make it so? The NNNAP says that you can use coercion when your life is in danger.
Yes, living is risky. Why is it OK for others to decide what risk I should take? In most cases I can leave, and that would be the right choice, but if I can't I'll have to rely on the NNNAP to save me.