When Legolas finally gives way to his anger, there is more to the fear behind it than meets the eye.
He says, "They are all going to die", when he wishes he could say, "You are going to die. I have already believed you dead once. Do not make it true this time".
Aragorn's reply is like a keen knife to the heart: "Then I shall die as one of them".
Legolas would say, if he could, "Then you would kill me too? For that will come with your death."
But he does not. He simply turns and walks away.