Lost Season 6 Episode 6

This conversation from tonight's episode drives me crazy...

Your friends, Shepherd and Reyes, do you know where they went?

No I don’t.  Why is Claire here?  And what was she talking about?

She’s a confused girl.  Under the influence of an angry man. 

What man?

For years, he has been trapped.  But now Jacob’s gone, he is free.  This man will not stop until he has destroyed every living thing on this island.  He is evil incarnate. 

And you want me to speak with him?

No.  I want you to kill him.  He will come to you as someone you know; someone who has died.  As soon as you see him, plunge this deep into his chest.  If you allow him to speak it is already too late.

Since I’ve been here, I’ve been drowned, beaten and tortured, at your hands.  Why would I ever do anything for you?

You said that there is still good in your soul.  Then prove it.

In what world is killing good?  And, to prove he's good, Sayid has to kill?  How does Sayid know the one asking him to kill is good? It makes no sense.  What makes even less sense is that when I hit play on the DVR and come back from commercial - Sayid will have accepted the conversation and gone out to see Locke.
I just can't get over how gullible or ? these people are.  I wouldn't have moved an inch until he explained himself to my satisfaction.  This is why Lost can be trying.