Since David is an outcast, he is more sensitive and sympathetic.  An example of this is when he tries to protect Sophie.

When David encounters Sophie, he is about ten years old.  He has never met anyone with a mutation before, and like most of his people he assumes that they are monsters.  When he meets the girl with six toes, he keeps her secret despite the fact that his father is the second generation founder of Waknuk.  Waknuk is extremely dictatorial, with anyone who does not fit into their narrow view of the world expelled.

 I tried to explain that a person with a deviation -- a small deviation, at any rate -- wasn't the monstrosity we had been told. (ch 6)

David is also different from others because he is telepathic.  So he realizes that Sophie needs to be protected, and he goes out of his way to try to keep her safe.

I ran up the stone and flung myself on him. He was bigger than I was, but it took him by surprise, and we went down together in a whirl of arms and legs. All I knew of fighting was what I had learnt from a few sharp scuffles. (ch 5)

David tries to fight Alan to protect Sophie because he can understand how she feels.  He knows she is just a normal little girl who got a bum rap from fate.  Without much of an interest in himself, he tries to fight a much bigger man just to buy her time.

David's deviation is much easier to hide than Sophie's, but he still understands how she feels.  He regrets betraying her, but he could not help it.  His father made sure of that.