Don't expect any mortality from him.

King has been mentally unstable even before his mother's death. He's being called ugly, animal, disappointment just for existing. After her death the severe neglect drove him to insanity ,we can literally see him banging his head on the wall as a kid and as an adult he keeps asking Sam to take control of him so that he won't act out his insanity. So I don't think any reader should expect basic morality from him because even before he went insane he didn't have any chance to have any morals because people kept treating him like an animal instead of a human child. He meet Sam after he went insane so expecting him to act rationally towards him is pointless. If you think of the king as a mental patient maybe it would easier to read this story otherwise we will all keep getting frustrated.