@Red225 :
"Zagan's moral backing is really superior to that nameless girl who he saved; the girl's words are meaningless. It doesn't matter if it is right or not for the weak to survive; the universe is not fair and does not care whether one is weak or not and there is no moral or ethical argument that will stop the vast majority of catastrophes that may befall a person. Being strong is something needs to do to survive, and that's all there is to it. Whether that be to have strength by joining with a group, paying dues to a government for protection, or have money or have talent or be so kind that others will spring to your aid. To bemoan other's strength is a sign that you have given up on protecting yourself."
First, I want to precise that when I talk to weak, strong and strength I talk about "the skills to protect yourself alone in any situation" It's the same meaning that Zagan and the nameless girl use when they talk about weak, strong and strength. So a tetraplegic being protected by the society (whatever the reason for it) isn't strong: it's a weak being protected.
With that said, there is a flaw in your post because you switch from the definition above (that you use for the first 2 and the last sentences) with another definition of strength which is: "how someone can protect himself" (which in this definition makes our tetraplegic's example as strong as the society want to protect him).
With Zagan definition, if you join a group to protect you, you gave up on protecting yourself (to an extent).
But by not having to rely on strength to survive, one can get more skills which would benefit the group more (specialization principle).
And in this regard, I think at the contrary that more often than not, the girl is right.
Moral and ethics are subjective so, in a vacuum, nothing is right or wrong. But what the girl ask isn't: "Is killing the weak a universal good ?" but more like "Is killing the weak a good thing for what you want ?".
At the first question, the answer is like you said: it doesn't matter. But at the second, the answer will tend toward: no, killing the weak isn't a good thing.
Because letting the weak live helps society better by allowing specializations in other fields than war, by allowing skill diversity and by facilitating socialisation between people.
In return, this "protection of the weak" helps groups to be formed, which upgrade the quality of life and develop communities stronger than the sum of their people.
So if you want to socialize with people, if you want an easier life or if you want to be safer it's often better to protect the weak for you (and to be protected by stronger people or group than you).
This doesn't negate what Zagan says, and doesn't prove him wrong: Zagan is a loner that want to live alone so for him being strong is the most important because his protection and life quality depend on it.