Wilfred: I'm sorry. Look, just leave me.The scene is far from a perfect parallel to the Agony in the Garden, of course. Christ is fully human, yes, but He is a sinless human - and also fully divine. The Doctor may be godlike to some, but he is a mortal and a sinner. Those are, in fact, vital parts of his story.
The Doctor: Okay, right then, I will. 'Cause you had to go in there, didn't you? You had to go in there and get stuck, oh yes. 'Cause that's who you are, Wilfred. You were always this, waiting for me, all this time.
Wilfred: No, really, just leave me. I'm an old man, Doctor. I've had my time.
The Doctor: Well, exactly, look at you, not remotely important. But me... I could do so much more. So much more! But this is what I get. My reward. But it's not fair!
I don't always see clearly where the line is between natural human reaction and sinful error. (Few of us this side of Heaven see it clearly, though we're meant to.) What I do see here, at least, is a very human reaction to a very unfair death.
The Doctor is right. It isn't fair. What more could he do in the universe if he let Wilfred die? What more could a saint like Maximillian Kolbe have done, if he'd not stepped up and sacrificed himself? What more could Christ do on earth if He turned down that cup of suffering? It isn't fair.
But, then, God is not fair, is He?
Thankfully, He is not. If God were fair, we'd be hopeless! C. S. Lewis put it well in his "myth retold", Til We Have Faces. In it, the pagan gods are going to accuse Redival of her sins. Her tutor replies that "(i)nfinite hopes--and fears--may both be yours. Be sure that, whatever else you get, you will not get justice" "Are the gods not just?" she asks. "Oh, no, child. What would become of us if they were?"
God is not just. He is merciful. We even see an image of that mercy in the site of the Doctor's sacrifice. Wilfred confesses his unworthiness, compared to the Doctor, from where? A little box. The Doctor, the healer, steps into the adjacent box and, there, releases Wilfred by taking on the penalty himself. Wilfred couldn't see the radiation around him that would take his life; nor can we see the sin that will take our eternal lives. In both cases, though, we need that little box, that confession, and that exchange. We need that unfair sacrifice to set us free